1 In A Medium Sized Bowl, Mix Corn Starch Into The Grated Cheese, So That The Cheese Is Coated, Set Aside. This Will Help The Cheese From Getting Too Stringy. 2 Bring 2 Quarts Of Water With The Tablespoon Of Salt To A Boil In Thick-Bottomed Saucepan. Add The Elbow Macaroni And Follow The Cooking Time Instructions On The Package, Minus About 2 Minutes. (If Your Macaroni Doesn'T Come With Instructions, Start Checking At 7 Minutes). Cook Until Al Dente - Cooked Through, But Still Slightly Firm. Drain The Water From The Cooking Pan. 3 While The Macaroni Is Cooking, Prepare The Sauce. Melt The Butter In A Large Saucepan On Medium Heat. Whisk In The Flour. Slowly Dribble In The Milk, While Whisking (To Avoid Clumping) Until The Sauce Is Smooth. Slowly Add The Grated Cheese, While Whisking, Until Smooth. Stir In The Lemon Juice. Add The Cooked, Drained Macaroni And Ham. Do Not Over-Mix. Sprinkle In Some Freshly Grated Black Pepper.