Cook the fettuccine noodles according to package instructions until al dente. Drain and set aside.
In a large skillet over medium heat, melt the butter. Add the minced garlic and sauté for about 1 minute, until fragrant but not browned.
Sprinkle the flour over the butter and garlic, whisking continuously for 1–2 minutes to form a smooth roux.
Gradually pour in the milk and heavy cream while whisking to prevent lumps. Season with salt and pepper to taste.
Simmer the sauce for 4–5 minutes, stirring occasionally, until it thickens slightly.
Stir in the grated Parmesan cheese until fully melted and the sauce becomes creamy. Taste and adjust seasoning if needed.
Add the cooked fettuccine noodles to the skillet and toss to coat evenly with the sauce.
Serve immediately, garnished with extra Parmesan or freshly chopped parsley if desired.
Enjoy!