Caramelized Onion Pasta

Creamy spaghetti with onions cooked down for half an hour, shrimp, Parmesan and a proper spoonful of chili crisp over the top.

Spaghetti, Chili Crisp and Onions Cooked Down for Half an Hour

Here is what the recipe card actually makes, because the name only tells you about a third of it. One large onion goes into butter and olive oil on medium-low for 30 minutes until it collapses and turns sweet. Ten shrimp get cooked in 2 tablespoons of chili oil with four sliced cloves of garlic. Then cream, Parmesan, 200g of pasta and a splash of the pasta water pull the two halves together, and the whole thing gets finished with more Parmesan, chives and more chili crisp. It feeds two and the card calls it 40 minutes.

So this is a creamy shrimp pasta as much as it is an onion one, and the chili oil is not a background note. It is doing a third of the work. Every finished photo on this page has chili crisp spooned over it, sediment and all, and that crunchy, savoury heat is what keeps half a cup of cream and half a cup of Parmesan from tasting flat.

Worth knowing before you start: 30 minutes on medium-low does not get you the dark mahogany onion jam you see in French onion soup. It gets you what the photos further down show, soft golden strands that have given up all their water and gone sweet. That is plenty for this sauce, and it is the honest version of the timing on the card. Chasing a darker colour in the same 30 minutes means turning the heat up, and that burns them instead.

What You Need, Including the Chives the Card Leaves Off the List

The card lists eleven ingredients, and three of them need a word before you shop: the chili oil is a bigger amount than the name suggests, the salt has nowhere obvious to go, and the chives in the final step are not on the list at all.

The onion base

• 1 tablespoon extra-virgin olive oil and 1 tablespoon unsalted butter: used together on purpose. The butter brings the flavour and the oil raises the smoke point, which is what lets you leave the pan alone for half an hour without the butter solids catching.
• 1 large onion, thinly sliced: a whole onion for two servings, and it needs to be sliced thin and evenly so it all collapses at the same rate. It cooks down to a fraction of what you see on the plate in the photo above.

The sauce

• 2 tablespoon chili oil: the card says 2 tablespoons, which is a real amount, and the photos show a chunky chili crisp rather than a clear infused oil. Use one with sediment in the jar and spoon up some of the solids, not just the oil floating on top.
• 4 garlic cloves, thinly sliced: sliced, not minced, so they stay distinct in the sauce instead of disappearing into it.
• 10 shrimp: peeled and deveined. They are in the card as a standard ingredient, not an optional one, and they are in every photo on this page.
• ½ cup heavy cream: the whole body of the sauce. Thickened cream works, it is what is in the ingredients photo.
• ½ cup grated Parmesan: grate it finely yourself if you can. The fine fluffy grate in the photo melts into the sauce in seconds, where a coarse shred sits in clumps.
• 200g pasta: see the section below on which shape to use, because the photos on this page answer that better than the usual advice does.

Finishing

• ¼ cup parsley, finely chopped: stirred through at the end, not sprinkled on top.
• 1 teaspoon salt: the card lists it to taste but never tells you where it goes. Put it in the pasta water, which is the only place in this recipe that salt can season anything from the inside.
• Chives: the card's last step tells you to garnish with chives and chives are not in its ingredient list, so buy them with everything else or you will be short at the end. Same for the extra Parmesan and extra chili oil that step calls for.

How to Make Caramelized Onion Pasta, Step by Step

One thing the card does not say, and it matters for the 40 minute total: start the pasta water while the onions are cooking. Done in strict order the steps take closer to 50 minutes, because the 30 minutes of onions and the 10 minutes of pasta are counted as if they overlap.

1. Heat a pan over medium heat. Add the olive oil and melt the butter in it.

2. Add the thinly sliced onions and cook over medium-low for 30 minutes, stirring often, until they collapse and turn golden and sweet. Set them aside. This is the step that decides the dish, so it is worth putting the timer on.

3. Cook the pasta in well salted boiling water until al dente, about 10 minutes. Reserve 1 cup of the pasta water before draining.
4. In the same pan, add the chili oil, garlic and shrimp. Cook until the shrimp is about 90% done. It only takes a couple of minutes and they finish cooking in the cream.

5. Add the heavy cream, then the caramelized onions, and stir to combine.

6. Add the pasta along with the Parmesan and ½ cup of the pasta water, and stir to combine. Add more of the reserved water a splash at a time until the sauce coats the strands. The card reserves a full cup and only uses half, so there is spare on purpose.

7. Add the chopped parsley and give it a final mix.

8. Serve in a bowl, grate over more Parmesan, and finish with chopped chives and another spoonful of chili oil.

Thirty Minutes of Onions, and What They Should Look Like

Keep the heat at medium-low and stir often. The two things that go wrong are the same two every time: the heat is too high, so the edges catch and go bitter before the middle softens, or the onions are sliced unevenly, so the thin bits burn while the thick bits are still crunchy. If they start browning too fast, add a splash of water to the pan, scrape the bottom and carry on. The water buys you time and lifts the sweet brown stuff off the base, which is where the flavour is.

Compare the two onion photos above. In the first they have softened and lost their volume but are still pale. In the second, at the end of the 30 minutes, they are collapsed, glossy and golden. That second photo is the target. If yours look like that, stop. Going further needs a lower heat and a lot more time, not a hotter pan.

You can cook the onions ahead. They keep in the fridge for a few days, and since they are the only slow part of this recipe, doing them on a Sunday turns this into a 15 minute dinner on a Tuesday.

Use the Spaghetti, Not the Penne

This page used to tell you to reach for penne or rigatoni and treat spaghetti as the fallback. The photos say otherwise. The ingredients shot has a box of spaghetti in it, and every process and finished photo on this page is spaghetti, so that is the shape this sauce was actually built around and tested on.

It makes sense when you look at the sauce. It is thin and glossy rather than thick and chunky, with nothing in it that needs catching in a tube. Long strands hold a cream sauce in a film along their whole length, which is exactly what you want here. Penne and rigatoni are better when there are chunks to trap. If spaghetti is what you have, you already have the right one.

A note on the name: caramelized onion pasta with chili crisp, cream and shrimp is not a traditional Italian dish and this page is not going to pretend otherwise. It is a fusion plate, which is the whole point of this site. The technique of cooking onions down slowly is borrowed from everywhere, and the chili crisp is what makes it taste like dinner here rather than a textbook.

What to Serve It With, and How It Keeps

It is rich, so the useful partners are the ones that cut through rather than add to it. Good options, each of which is already on your table or close to it:

• Lemon zest or a squeeze of juice over the top. Half a cup of cream and half a cup of Parmesan is a lot of fat, and acid is the fastest fix.
• A sharp green salad, dressed with more vinegar than you would normally use.
• Garlic bread, for the sauce left in the bowl, which there will be.
• Extra chili crisp on the table, so people can take it as hot as they want rather than you deciding for them.

Leftovers go in an airtight container in the fridge. Reheat gently in a pan over low heat with a splash of cream or water, stirring as it loosens. A cream and Parmesan sauce will split if you blast it, and the microwave is the most reliable way to split it. Cold from the fridge the sauce sets solid, which is normal and comes back together with the splash of liquid.

The shrimp are the part that suffers on day two, so if you know you will have leftovers, it is worth cooking the shrimp fresh for the second serve rather than reheating them twice.

Frequently Asked Questions

What kind of pasta should I use?

Spaghetti. That is what every photo on this page uses and what the sauce was built for, because it is a thin glossy cream sauce that coats long strands well. Penne, rigatoni and linguine all work if that is what is in the cupboard, but spaghetti is not the compromise here, it is the first choice.

How do I prevent the onions from burning?

Keep the heat on medium-low and stir often, and slice the onion evenly so it all cooks at the same rate. The butter and olive oil together stop the pan catching. If the edges start browning faster than the rest, add a splash of water, scrape the base and keep going.

Can I add protein to this dish?

The recipe already has it: 10 shrimp are in the card and in every photo. If you want something else instead, seared salmon or sliced chicken both suit a cream and chili oil sauce. Cook it the same way the shrimp are cooked, in the chili oil and garlic, so the fat picks up the heat before the cream goes in. If you want to go further, there is a Marry Me Shrimp Pasta on this site built on the same cream and Parmesan base, with sun dried tomatoes instead of onions.

How do I store leftovers?

In an airtight container in the fridge. Reheat in a pan over low heat with a splash of cream or water and stir as it loosens, rather than in the microwave, which splits the sauce.

Can I make this dish vegan?

Most of it, yes, but read the card first: it has 10 shrimp in it, so a vegan version means leaving those out, not just swapping the dairy. Use a vegan butter, a plant based cream and a vegan Parmesan or none at all. Without the shrimp the onions and the chili oil carry the dish, so go heavier on both, and use the full 2 tablespoons of chili oil rather than less.

Is this the same as the caramelized onion ramen on this site?

Close, and worth knowing about. Creamy Caramelized Onion Shrimp Ramen uses the same onion, the same four cloves of garlic, the same 10 shrimp and the same cream, with gochujang stirred in and instant ramen instead of spaghetti. Miso Caramelised Onion Ramen is the same idea again with miso paste. If you like this one, those are the next two, and if you are out of pasta either works with a packet of instant noodles.

For more chili oil in a pasta pan, Chili Oil Vodka Pasta takes the tomato route instead of the cream and onion one. The rest of the noodle and pasta recipes here live in the Asian noodle recipes collection.

Caramelised Onion Pasta

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Savor the sweet allure of caramelised onions twirled in rich, creamy pasta.

• Author: Genio Ng
• Prep Time: 10 minutes
• Cook Time: 30 Minutes
• Total Time: 40 minutes
• Yield: 2 1x
• Category: Pasta
• Method: Easy
• Cuisine: Italian

Ingredients

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• 1 Tbsp. extra-virgin olive oil
• 1 Tbsp. unsalted butter
• 1 large onion, thinly sliced
• 4 garlic cloves, thinly sliced
• 2 tbsp of chili oil
• 10 shrimps
• ½ cup of heavy cream
• ½ cup of parmesan cheese, grated
• ¼ cup of parsley, finely chopped 
• 200g of pasta
• 1 tsp of salt - to taste

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Instructions

1. Heat a pan over medium heat. Add the olive oil and melt the butter in a pan. 
2. Add the thinly sliced onions and cook over medium-low heat for 30 minutes. Stir every minute until it is caramelized. Set aside.
3. Cook the pasta in hot boiling water until al dente for 10 minutes. Set 1 cup of pasta water on the side.
4. In the same pan, add the chili oil, garlic and shrimp. Cook until the shrimp is 90% cooked.
5. Then, add heavy creamy followed by caramelized onions and stir to combine.
6. Add the pasta along with parmesan cheese and ½ cup of pasta water ( adjust the consistency of the sauce to your liking). Stir to combine.
7. Next, add chopped parsley and give it a final mix. 
8. Serve in a bowl, grate more parmesan cheese, garnish with chives and more chili oil. Enjoy! 

Genio Ng

Hi there, I'm Genio. I really appreciate you taking your time and visiting me here. As an international student from Indonesia coming to Sydney right after Covid lockdown - it was challenging for me to make friends and find myself in a new city. I've never cooked before but I found my passion in food content creation and testing Asian inspired recipes - I learnt that cooking can be incredibly easy, cheap and fun so I'm super happy to be able to share this with you! Please come by my socials and say Hi - always keen to make new friends! Genio

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