Put 1 tbsp of olive oil into a pan and get it hot. Add sausage and brown until it is only slightly pink inside. Don't worry about cooking it a little longer if you are worried about it being undercooked, the fat content of the sausage will keep it from drying out. When sausage is done set aside in a bowl.

Meanwhile, heat 1 tablespoon of the butter and the oil in a large skillet over medium heat. Add the mushrooms, season with salt and pepper, and sauté until browned and tender, about 5 minutes. Add the garlic and remaining 2 tablespoons butter and sauté for 1 minute more. When done put into the same bowl as the sausage.

If you are using Gluten free pasta it is very important that you do not overcook it or it will become mushy and fall apart. I really like Manini's brand because it comes as fresh pasta in Whole Foods and only needs a few minutes to cook. Bring a large pot of salted water (add more salt than you think, like 2 tablespooons) to a boil. Add the pasta and cook until al dente, 3 - 5 minutes but check the packaging for precise timing. Drain with a colander when done.

Add the cooked spaghetti, sausage, and mushrooms into the pan with 1 tbsp of olive oil. Toss and stir until everything is nicely combined. Add the grated cheese and continue to toss for another minute or two. Remove pasta with mushrooms and sausage and put in a big bowl. Add the parsley and toss once more to combine. Serve with additional grated cheese to the liking of each of your guests.