Cook the fettuccine pasta in salted boiling water according to package instructions until al dente. Drain and set aside.
In a large skillet, melt the butter over medium heat.
Add minced garlic and sauté until fragrant, about 1 minute.
Pour in the heavy cream and bring to a gentle simmer.
Reduce heat to low and stir in the grated Parmesan cheese until the sauce is smooth.
Season with salt, black pepper, and red pepper flakes if using.
Add the cooked pasta to the skillet and toss to coat evenly with the sauce.
Garnish with chopped parsley and serve immediately.