Cook the pasta in a large pot of salted boiling water until al dente. Reserve ½ cup of the cooking water, drain, and reserve.
In a large skillet over medium-high heat, melt the butter with the olive oil.
Saute the mushrooms until brown and most of the liquid has evaporated. Add minced garlic, two tablespoons of chopped parsley, and red pepper flakes.
Deglaze the skillet with white wine and simmer until reduced by half. Stir in the chicken stock, heavy cream, and parmesan cheese.
Simmer for about 5 minutes until the sauce thickens.
Mix in the drained fettuccine and serve with extra parmesan cheese and the remaining tablespoon of parsley on top. If the sauce is too thick, thin it out with a bit of the reserved pasta cooking water.