Pasta with Mushroom Cream Sauce

I'm posting this mostly so I will have a link to it since it is a recipe I made up based on a couple other recipes and I love the way this turned out.  I made it once for my cooking club and again the other night.  I forgot how yummy it was and I want to have the recipe saved on the internet for my future reference!

Mushroom Cream Sauce

2 tablespoons unsalted butter

1/2 cup diced shallots

5 sage leaves

Salt and pepper, to taste

8 ounces portobello mushrooms, sliced

1 cup heavy cream

1/2-3/4 cup mushroom stock

1/2 leek, roughly chopped

baby arugula

Parmesan cheese

Melt butter in a saute pan over medium heat. Add mushrooms, shallots and sage. Season with salt and pepper. Cook 7 minutes until slightly softened. Pour in cream and 1/2 cup mushroom stock and heat slowly. When the sauce has reached a velvety smooth consistency, remove from stove. If sauce is too thick, add more stock to reach desired consistency.  Add pasta to sauce and stir in leek and arugula and cook until arugula wilts.  Serve with a sprinkle of parmesan cheese.