1 Mix The Corn Starch With The 2 Cheeses In A Bowl And Set Aside. The Corn Starch Will Help Prevent The Cheese Sauce From Getting Too Stringy. 2 Put The Milk Into A Small Saucepan And Heat Until Steamy. Keep Warm While You Are Preparing The Recipe, Do Not Let Boil. 3 Put 2 Quarts Of Water, Salted With 1 Tbsp Salt, Into A Large Pot And Heat To A Boil. Once The Water Is At A Full Boil, Add The Macaroni To The Pot. Return To A Boil, And Cook, Uncovered, For About 2 Minutes Less Than The Macaroni Package Specifies, So That It Is Al Dente, Cooked, But Still Firm To The Bite. 4 While The Water Is Heating And The Macaroni Cooking, Prepare The Chorizo Cheese Sauce. Remove Chorizo From Its Casing And Put Into A Medium Thick-Bottomed Saucepan On Medium High Heat. When The Chorizo Begins To Sizzle, Reduce The Heat To Medium. Cook The Chorizo, Stirring Often, For 2 Minutes. Add The Minced Red Onion And Cook The Mixture Until The Onions Soften, About 3-4 Minutes. 5 When The Macaroni Is Cooked, But Still A Bit Firm, Drain It And Set Aside. Preheat Oven To 375