Boil a large pot of salted water and cook the pasta according to the package instructions until al dente. Reserve ½ cup of the pasta water before draining.
In a large skillet, heat the olive oil over medium heat.
Add the sliced leeks and cook for 6-8 minutes, stirring occasionally, until they are soft and golden.
Stir in the mushrooms and cook for another 5-7 minutes until tender and slightly browned.
Add the minced garlic and sauté for 1 minute until fragrant.
Pour in the white cooking broth and stir, scraping up any browned bits from the bottom of the skillet. Let it simmer for 2 minutes.
Stir in the heavy cream, reducing the heat to low, and let the mixture simmer for 3-4 minutes until slightly thickened.
Gradually stir in the Gruyere cheese, allowing it to melt completely into the sauce. Season with salt and pepper to taste.
Toss the cooked pasta in the skillet with the sauce, adding reserved pasta water as needed to achieve your desired consistency.
Sprinkle with chopped parsley, if desired, and serve immediately.
