In a large deep skillet on medium-high heat, melt the butter and fry the mushrooms in it until they are cooked and have released most of their moisture. Add in the garlic, fry until fragrant and browned, around 2 minutes, Add in the peas and warm up.
Whisk in the whipping cream until combined.
Stir in the Parmesan cheese, mixing it into the cream sauce until it melts into the sauce.
Stir in the cooked fettuccine noodles and simmer until the noodles are hot.