In large frying pan, sauté garlic, onion, and mushrooms in 1 stick butter over medium-high heat until mushrooms are about 1/2 cooked. Add shrimp and additional stick of butter, sauté until shrimp are pink and fully cooked. Add pasta, toss lightly until coated with butter mixture. Serve with grated Parmesan cheese and garlic bread. For those who like tomatoes in their scampi, add 1-14 oz can drained plain chopped or stewed tomatoes in place of the second stick of butter and decrease the first addition of butter to 2 tbsp. * Using cooked shrimp is not recommended, as it tends to get rubbery and tough when cooked in this recipe.