Begin by bringing a large pot of salted water to a boil. Add your favorite pasta and cook according to package instructions until al dente, usually about 8-10 minutes. Once cooked, drain the pasta in a colander, reserving a cup of the pasta water, and set it aside while you prepare the sauce.

In a large skillet, melt 2 tablespoons of butter over medium heat. Add the sliced leeks and sauté them gently for about 10-12 minutes, stirring occasionally, until golden-brown and aromatic.

Once the leeks are caramelized, add the sliced mushrooms to the skillet. Stir them in and continue to cook for another 5-7 minutes until tender and moisture has evaporated.

Reduce the heat to low and pour in 1 cup of heavy cream, stirring to combine with the leeks and mushrooms. Gradually sprinkle in the grated Gruyere cheese, stirring continuously until melted and creamy.

Add the drained pasta into the skillet with the creamy sauce, tossing gently to coat. If the sauce is too thick, stir in reserved pasta water to reach desired consistency. Season with salt and pepper to taste.

Transfer the pasta to serving bowls and garnish with additional grated Gruyere cheese or fresh herbs like parsley. Serve immediately.