Melt butter in a large wide skillet over medium-low heat. Add minced garlic and cook for 2 minutes, stirring often, until soft and fragrant. Do not let it brown.
Pour in the heavy cream and stir to combine. Increase heat to medium and bring to a gentle simmer. Cook for 4–5 minutes, stirring occasionally, until the cream reduces slightly and coats the back of a spoon.
Reduce heat to low. Add parmesan in 2–3 batches, stirring well between each addition until fully melted and smooth. Stir in white pepper, garlic powder, and nutmeg. Taste and season with salt as needed.
Add drained fettuccine directly to the skillet. Toss over low heat until the sauce clings to every strand. Add reserved pasta water one tablespoon at a time if the sauce needs loosening.
Divide between bowls. Top with extra parmesan, cracked black pepper, and fresh basil. Serve immediately.
