Cook the pasta in heavily salted boiling water (the water should taste salty) until it's slightly underdone. Drain it over a bowl to catch the pasta water. Reserve 1 cup of the pasta water and rinse the noodles with cold water in the sink to keep them from continuing to cook.
Add the mushroom ragu, cream or half and half, ½ cup of the reserved pasta water, and the grated parmesan to a skillet. Set it over medium heat and cook, stirring until the cheese is melted and the sauce is simmering.
Add the pasta to the skillet, tossing it around in the sauce to coat. Cook until noodles are al dente, adding as much more of the reserved pasta cooking liquid as you like to achieve a saucy consistency.
Pile the pasta onto plates and top with black pepper and fresh herbs.
