Step 1: Bring a large pot of salted water to a boil and cook fettuccine according to package instructions until al dente. Reserve 1/4 cup pasta water before draining.

Step 2: Heat olive oil and butter in a large skillet over medium heat until melted.

Step 3: Add sliced mushrooms in a single layer and cook without stirring for 3 to 4 minutes until browned.

Step 4: Stir mushrooms and continue cooking until tender and golden.

Step 5: Add minced garlic and dried thyme, cooking for about 30 seconds until fragrant.

Step 6: Season with salt and black pepper to taste.

Step 7: Add cooked fettuccine to the skillet along with reserved pasta water.

Step 8: Toss gently to coat pasta and loosen the sauce.

Step 9: Remove from heat and stir in grated Parmesan until creamy and well combined.