Prep your ingredients: Start by preparing all your ingredients. Slice the leeks thinly, making sure to wash them well. Slice the mushrooms, mince the garlic, and grate the Gruyère. Bring a pot of salted water to a boil for the pasta.

Cook the pasta: While you’re working on the sauce, cook your pasta according to the package instructions. Make sure to reserve about a cup of pasta water before draining.

Caramelize the leeks: In a large skillet, heat the olive oil over medium heat. Add the sliced leeks and sauté them for about 10-12 minutes, stirring occasionally, until they turn golden brown and soft.

Cook the mushrooms: Once the leeks are beautifully caramelized, add the sliced mushrooms to the pan. Cook them for 5-7 minutes, allowing them to soften and release their juices. Stir in the garlic and cook for another minute.

Deglaze the pan: Add the dry white wine (or vegetable broth) to the pan to deglaze it. Use a wooden spoon to scrape up any browned bits from the bottom of the pan. Let the wine reduce by half for about 2-3 minutes.

Make the sauce: Lower the heat and add the heavy cream to the pan, stirring to combine. Bring the mixture to a simmer, and let it cook for 3-5 minutes until it thickens slightly.

Add the cheese: Stir in the grated Gruyère cheese and continue to cook, stirring frequently, until the cheese is melted and the sauce is creamy. Season with salt and pepper to taste.

Combine pasta and sauce: Add the cooked pasta to the skillet with the sauce. Toss everything together, adding a bit of reserved pasta water if the sauce is too thick.

Garnish and serve: Serve the pasta hot, garnished with fresh parsley and a sprinkle of extra Gruyère if desired.