Begin by slicing the leeks thinly, discarding the tough green tops, then rinse them thoroughly under cold water to remove any dirt trapped between layers.
Heat the large skillet over medium-low heat and add the butter. Once melted, add the sliced leeks along with a pinch of salt.
Cook the leeks slowly, stirring gently every few minutes, until they turn a beautiful golden caramel color and smell sweet, about 20-25 minutes.
While the leeks cook, bring a large pot of salted water to a boil. Add your pasta and cook until al dente, about 8-10 minutes.
Drain the pasta, reserving about a cup of the pasta water, then add the cooked pasta directly into the skillet with the caramelized leeks.
Pour in the heavy cream and stir gently to coat the pasta and leeks evenly. Let it simmer for 2-3 minutes until warmed through.
Stir in the grated Parmesan cheese until melted and the sauce slightly thickens. If the sauce feels too thick, loosen it with a splash of the reserved pasta water.
Add a teaspoon of lemon juice and season generously with salt and freshly cracked pepper, then stir to combine.
Remove the skillet from heat and let the dish rest for a minute to allow flavors to meld. Taste and adjust the seasoning if needed.
Serve the pasta hot, garnished with extra Parmesan and a drizzle of olive oil if desired. Enjoy the rich, silky texture and the subtle sweetness of the caramelized leeks.
