Sprinkle the flour over the garlic, and cook 30 seconds, stirring constantly.
Reduce the heat to medium and gradually add milk, stirring constantly. Cook until the sauce slightly thickens (about 2-3 minutes). Keep stirring and scraping the bottom of the pan, because you don't want the milk to "scorch" on the bottom of the pan. Keep it moving!
Once the sauce has thickened, remove the pan from heat, and add half of the cheese to the sauce, stirring until it melts.
Add the hot prepared pasta, or raw zucchini, to the pan, and toss well to combine; or plate the pasta or zucchini and top with the alfredo sauce.
Top with the cooked bacon, and add freshly ground pepper, and parsley if using.
Notes
Mix fresh raw zucchini noodles into the pasta and get your veggie serving for the meal!
Recipe by My Utensil Crock at https://www.myutensilcrock.com/2017/10/15/healthier-fettuccine-alfredo/