How to Make It
Preheat oven to 300°F. Combine cheese and cornstarch in a medium saucepan. Stir in evaporated milk and hot sauce; cook, whisking constantly, over low until sauce is bubbly and well combined, about 5 minutes. Remove from heat; keep warm.
Wrap rolls in aluminum foil; bake in preheated oven until thoroughly heated, about 10 minutes.
Meanwhile, combine sour cream, mayonnaise, chives, horseradish, lemon juice, salt, and pepper in a small bowl. Spread sour cream mixture on cut sides of bottom halves of rolls; top each with 4 ounces Beef, and drizzle each with 3 tablespoons Cheddar sauce. Cover with top halves of rolls; serve immediately with remaining Cheddar sauce, if desired.