In a large pot of boiling salted water, cook pasta according to package instructions; drain well.
Heat olive oil in a large skillet over medium heat. Add breadcrumbs and cook, stirring, until browned and toasted, about 3-5 minutes; season with salt and pepper, to taste. Set aside.
Melt butter in the skillet over low heat, 1 tablespoon at a time, until the butter starts to foam. Add garlic to the skillet, and cook, stirring frequently, until fragrant, about 1 minute.
Stir in mushrooms and thyme, and cook, stirring occasionally, until mushrooms are tender and browned, about 3-5 minutes; season with salt and pepper, to taste.
Serve pasta immediately, topped with mushroom-butter mixture and breadcrumbs, garnished with parsley, if desired.