Cook the fettuccine according to package instructions until al dente.
In a large skillet, heat olive oil over medium heat.
Add sliced mushrooms to the skillet and sauté for 5-7 minutes until browned.
Add minced garlic and sauté for an additional minute until fragrant.
Stir in fresh spinach and cook until wilted, about 2-3 minutes.
Pour in the heavy cream and bring to a simmer.
Add grated Parmesan cheese, stirring until melted and smooth.
Add the cooked fettuccine to the skillet, tossing to combine.
If the sauce is too thick, add reserved pasta water a bit at a time to reach desired consistency.
Season with salt and black pepper to taste before serving warm.