Pasta with Sous Vide Leeks and Pancetta

An interest sous-vide experiment with leeks turned into a creamy pasta sauce!

The inspiration comes from a recent post from Stefan’s Gourmet Blog, a Dutch blog (in English) I follow for a nice mix of posts on homemade Italian food, fine dining, and sous vide cooking.

Given the egg allergy of our son, he is missing out on the good old Pasta alla Carbonara. We sometimes do a Pasta alla Gricia (which uses the emulsion of the bacon fat, Pecorino cheese, and starchy pasta water to form an ultra-rich creamy sauce) as an alternative. New ideas for creamy and egg-free sauces are therefore always welcomed, especially when vegetable-based, like this one with sous-vide cooked and then pureed leeks.

Cooking leeks sous vide for 2 hours makes leeks sweet, luscious, and creamy. And that works very well with savory bits of slightly crunchy pancetta and the nice bite of spaghetti (provided that is cooked properly al dente). This is a quick dish if you cook the leeks sous-vide beforehand (and even cooking the leeks is simple, it just takes two hours of waiting for them to be done).

Mouthwatering narrative, right? We obviously needed to double the quantities of this 5-ingredient recipe to serve 4 persons:

• 4 large leeks (about 900g or 2 lbs after cleaning)
• 400g / 14 oz dried spaghetti
• 200g / 7 oz pancetta, diced
• 100g / 3½ oz freshly grated Parmesan
• 2 tbsp butter

We did not follow the recipe to the letter. As the leeks at my greengrocer were medium-sized, I bought 5 instead of 4, which was still short by quite a bit. As I trimmed the leeks a bit more than Stefan – to avoid any sand deposits at the base where the green parts start – I ended up with only 650g / 23oz instead of the 900g / 2lbs that Stefan would use for 4 persons. I compensated by adding about 200g / 7oz of leftover sauteed Italian stirfry vegetables when adding the pureed leeks and cheese mixture to the pancetta to heat through. As expected, it complimented the dish very nicely. Additionally, rather than using storebought spaghetti, I made fresh linguini, cooked al dente as well.

1. Remove the bottoms, and dark green tops of the leeks and vacuum seal the leeks and cook the leeks sous-vide for 2 hours at 85℃/185℉. 
2. When the leeks are (almost) done, bring a large pot of water to a boil. When the water boils, add salt and the pasta and let it cook the al dente time mentioned on the packaging.
3. In the meantime, melt the butter in a frying pan over medium heat. Add the diced pancetta and stir until crispy on the outside but still soft on the inside.
4. Take the leeks out of the sous vide bag and put them in a food processor and process until entirely smooth. Then add the freshly grated Parmesan and blitz to incorporate the cheese.
5. Add the pureed leeks mixture to the pancetta pan and stir over medium heat until heated through, then turn the heat to low. Season to taste with salt and freshly ground black pepper.
6. Drain the pasta (do not rinse!) and add it to the pan and toss until the spaghetti is coated with leeks sauce.
7. Serve immediately, sprinkled with some more freshly grated Parmesan and freshly ground black pepper.

The consistency of my pureed leeks and cheese mixture turned out really thick. It was almost Dutch split pea soup consistency; a spoon would almost keep standing upright on its own! Likely, I should have cut back on the doubled quantity Parmesan at the blending stage. Despite trying to dilute it to a more sauce-like consistency with the pasta water, it still turned out quite dense and not velvety smooth like a carbonara sauce. The dish tasted terrific though, and both kids loved it.

Next time, however, I will be taking out the fried pancetta from the pan and adding it back at the very last moment to better preserve their crispiness.