If you purchased whole mushrooms, clean and slice them.
Cook:
Cook the pasta following the instructions on the box. When the pasta is ready, reserve 1-cup of the pasta water and drain it.
While the pasta cooks, melt the butter in a skillet and add the minced garlic, mushrooms, Italian seasoning, salt, and red pepper flakes. Sauté for about 10 minutes, until the mushrooms are soft and have turned into a rich, deep brown color.
Combine:
Add the pasta to the skillet. Then, add the olive oil and Parmesan cheese. Use kitchen tongs to coat all the pasta with the garlic-butter sauce and mushrooms while distributing the olive oil throughout. This is a "coating" more than a "sauce." To make it saucier, slowly add the reserved pasta water (heat it in the microwave if it's not hot) to the skillet, toss to coat, and turn it into a sauce.