Boil a large pot of salted water, add fettuccine, and cook until al dente (8-10 minutes). Reserve 1 cup of pasta water before draining.

In the same pot, reduce heat to medium-low and melt butter. Add minced garlic and sauté until fragrant (1-2 minutes).

Pour in heavy cream and bring to a gentle simmer. Stir in salt, black pepper, and nutmeg. Simmer for 2 minutes, stirring regularly.

Gradually add Parmigiano Reggiano cheese, stirring until fully melted and sauce is creamy (2-3 minutes).

Mix drained fettuccine in the pot with the sauce, tossing gently to coat. Add reserved pasta water if sauce is too thick.

Taste and adjust seasoning if necessary. Serve immediately, garnished with parsley if desired.