Start with a whole onion chopped add that to a warm skillet of 3 tablespoons of butter and olive oil. Add 4 chopped garlic cloves sautee for 3 minutes, add the Italian sausage, cook for 8 minutes. Optional- at this point go ahead and add chopped mushrooms and cook for 5 minutes. Add the tomato sauce, salt and pepper to taste and simmer for 20 minutes. Add cream, Parmesan cheese, chopped basil.