Step 1: Cook the Pasta - Bring a large pot of salted water to a boil. Add the fettuccine noodles and cook according to the package instructions until al dente. Reserve about a cup of pasta water, then drain the noodles and set aside.
Step 2: Make the Roux - In a large skillet over medium heat, melt the butter. Add minced garlic and sauté for about a minute until fragrant. Whisk in the flour, stirring continuously for about 2 minutes to create a roux.
Step 3: Create the Sauce - Gradually pour in the heavy cream and milk, whisking continuously to avoid lumps. Allow to come to a gentle simmer, then reduce the heat to low as it thickens.
Step 4: Add the Cheese - Once thickened, slowly stir in the Parmesan and Romano cheeses until melted and the sauce is smooth.
Step 5: Combine the Pasta and Sauce - Add the drained fettuccine to the skillet with the sauce. Toss to coat evenly, adding reserved pasta water if needed to reach desired consistency.
Step 6: Garnish and Serve - Serve immediately, garnished with freshly chopped parsley. Enjoy with a side salad or garlic bread!