Cook spaghetti in a large pot of salted boiling water according to package directions, then drain and set aside.

Reserve about half a cup of the pasta water, which can be added to the sauce later if needed.

Heat olive oil in a large pan over medium heat and sauté minced garlic until fragrant, about 30 seconds.

Add sliced mushrooms to the pan and cook until softened and browned, which takes about 5-7 minutes.

Stir in the fresh spinach and cook until it wilts completely, which usually happens in 2-3 minutes.

Pour in the heavy cream and bring the mixture to a gentle simmer, allowing it to cook for 1-2 minutes until slightly thickened.

Add the cooked spaghetti to the pan with the sauce and toss to combine, ensuring all pasta is coated.

Stir in the grated Parmesan cheese and black pepper, and season with salt to taste.

If the sauce is too thick, add a splash of the reserved pasta water to reach your desired consistency.

Serve immediately, garnished with extra Parmesan and fresh parsley if desired.