Make the cheese sauce: Toss the cheese and cornstarch together in a bowl until totally coated. Set a medium saucepan over low heat. Add the evaporated milk. Once the milk is warm, whisk in the cheese mixture and cook, stirring constantly, until all the cheese is melted and the sauce is silky and smooth, about 5 minutes. Season with salt and pepper.
Cook the beef: Heat a large skillet over medium-high heat. Add the butter and ground beef and cook, stirring, until the exterior is caramelized and the inside is just cooked through, about 10 minutes. Season with salt and pepper and keep warm over low heat.
Assemble the cups: Fry or bake the tots as the label directs. Divide the warm tots among small cups and top with about a tablespoon of the cheese sauce, then a tablespoon of the ground beef. Top each with a small squiggle of ketchup and mustard and nally a pickle on top and a light sprinkle of sesame seeds.