Begin by bringing a large pot of salted water to a rolling boil. Add your chosen pasta, stirring gently, and cook until al dente, about 8-10 minutes. Reserve about 1 cup of the cooking water before draining the pasta in a colander. Set the pasta aside, letting it rest while you prepare the sauce.

In a large skillet, melt 2 tablespoons of butter over medium-low heat. Once melted, add the sliced leeks, stirring to coat them in the butter. Cook slowly for about 10-12 minutes, maintaining a low heat, until they have softened and turned golden brown.

Next, stir in 8 ounces of sliced mushrooms into the skillet with the caramelized leeks. Season generously with salt and pepper, and sauté for an additional 5-7 minutes, until the mushrooms are tender.

Pour in 1 cup of heavy cream, stirring continuously to combine it with the leeks and mushrooms. Gradually add 1 cup of grated Gruyere cheese, mixing until the cheese melts completely.

Add the drained pasta to the skillet, tossing gently to coat every strand in the sauce. Cook together on low heat for another 2-3 minutes.

Plate the pasta into bowls, ensuring an even distribution of the creamy mixture. Garnish with additional grated Gruyere cheese or fresh herbs.