Begin by cleaning and slicing the leeks, discarding the tough green tops. Thinly slice the mushrooms, and set them aside. Measure out the Gruyere cheese and heavy cream.

In a large skillet, melt the butter over medium heat. Add the sliced leeks, sprinkle with salt, and sauté for about 10-15 minutes until golden brown.

Once leeks are caramelized, add the sliced mushrooms to the skillet and cook for an additional 5-7 minutes until tender and browned.

Reduce heat to low, stir in the heavy cream and Gruyere cheese, allowing to simmer for 3-5 minutes until thickened.

Cook pasta according to package directions until al dente. Reserve about 1 cup of the pasta cooking water, then drain. Toss with the sauce in the skillet.

Plate immediately, garnishing with more Gruyere cheese and herbs if desired. Serve warm.