In a large pan, melt the butter over medium heat.
Stir in the garlic and sauté for 1–2 minutes, just until fragrant. Don’t let it brown.
Pour in the heavy cream, salt, and white pepper. Stir it up and let it warm for about 2–3 minutes.
Slowly whisk in the parmesan cheese, stirring constantly until it’s fully melted and smooth.
Add in the mozzarella and continue stirring until you have a thick, creamy sauce.
Serve over hot cooked fettuccine and sprinkle with chopped parsley if you’d like.