Cook bacon in a large skillet over medium heat until crisp; remove bacon, reserving 2 tablespoons drippings in skillet. Crumble bacon.
Saute sliced mushrooms and garlic in reserved drippings 3 minutes or until tender. Stir in pasta, Parmesan cheese, whipping cream, and pepper; simmer over medium-low heat, stirring often, until sauce is thickened. Stir in bacon and sliced green onions; serve immediately.