Melt the butter beautifully in a large skillet over a medium heat. Saute the mushrooms and garlic until both are a nice golden brown. Next, stir in the clams and juice, salt and white pepper, and don’t forget your parsley! Cook your concoction over medium heat until nice and hot. Toss everything together with your precooked pasta until it’s all evenly coated. Serve up your dish with a garnish of Parmesan cheese.