If you want to lighten the alfredo sauce to reduce fat and calories, we highly recommend substituting evaporated milk for the whipping cream. However, if you only have milk on hand, it can work. Simply bring all of the ingredients to a simmer. Remove 1/4 cup of the warm sauce and mix well with 1-2 Tbsp of all-purpose flour to make a roux. Blend the roux in with the remaining sauce until it reaches the desired thickness. You can also add a touch of cream cheese to help thicken your alfredo sauce too. While you technically could make alfredo sauce with milk, you'll be losing a lot of the rich creamy flavor the dish is popular for. To thicken your alfredo with half 'n' half, use 1 Tbsp of flour.