1. Preheat grill to medium heat. Lightly shape beef into eight 1/2 inch thick mini patties. Use your thumb to make and indentation in the center of each patty. Sprinkle evenly with salt and pepper.
Grill patties, covered, 7 to 10 minutes until a thermometer inserted horizontally into the center of a patty registers 160 degrees. Turning occasionally. Top each patty with two piece of cheese (half a slice for each patty) and remove from the grill.
Top each bottom bun with 1 patty , 1 lettuce leaf and 1 tomato slice. Spread1 tablespoon guacamole over each but top; sliders with bun tops.