Melt half the butter over a medium heat and add half the garlic. Cook for a couple of minutes then add the mushrooms and thyme and fry for about 10 minutes until softened. Scoop out the mushrooms and set aside.
Add the rest of the butter, melt and then add the rest of the garlic and the flour. Cook for a couple of minutes then slowly pour in the cream and whisk. Simmer until thickened.
Add the pasta and mushrooms plus a little pasta water, add a tablespoon at a time, until everything is coated and the sauce is the desired consistency. Serve sprinkled with thyme and black pepper.
Nutrition information is an estimate and will vary depending on the ingredients used.