Cook the pasta in plenty of salted boiling water according to the packet instructions. Before draining, save a mugful of the pasta cooking water.
While the pasta cooks, heat the olive oil and half the butter in a large frying pan over medium-high heat. Add the mushrooms and cook for 5-6 minutes without stirring too much - let them get golden.
Add the sliced garlic and thyme. Cook for 2 minutes until the garlic is golden and fragrant.
Season well with salt and plenty of black pepper.
Add the drained pasta to the pan with the remaining butter and a splash of the reserved pasta water. Toss everything together over the heat for 1-2 minutes until the pasta is coated in a silky sauce.
Serve topped with parmesan and chopped parsley.