01 -
Bring a large pot of well-salted water to a boil. Cook the fettuccine until al dente, then reserve 1 cup of pasta water and drain.
02 -
Melt the butter in a large skillet over medium heat. Add the garlic and cook for 30-45 seconds, stirring often, until fragrant but not browned.
03 -
Whisk in the flour and cook for 1 minute. The mixture should look smooth and pale, with no dry flour left in the pan.
04 -
Slowly whisk in the heavy cream, then the milk. Cook for 3-5 minutes, stirring often, until the sauce is steaming and lightly thickened.
05 -
Turn the heat to low or remove the pan from the burner. Add the Parmesan in small handfuls, whisking until smooth before adding more. Season with salt and pepper.
06 -
Add the drained fettuccine to the sauce and toss with tongs until coated. Add reserved pasta water a few tablespoons at a time until the sauce is glossy and loose enough to coat the noodles.
07 -
Taste and adjust the seasoning. Serve immediately with parsley, extra black pepper, and more Parmesan if desired.