1. Tear one hamburger bun into pieces. Place in food processor or blender container. Cover; pulse on and off, to form fine crumbs. 2. Combine bread crumbs, beef, garlic and chili powder in medium bowl, mixing lightly but thoroughly. Lightly shape into eight 1/2-in. thick mini patties. 3. Place patties on grill over medium, ash-covered coals. Grill, covered, 8 to 9 min. (over medium heat on preheated gas grill, 9 to 10 min.) until instant-read thermometer inserted horizontally into center registers 160°F, turning occasionally. Evenly top with cheese during last minute of grilling. 4. Place burgers on bottoms of remaining eight buns. Top with desired Toppings. Close sandwiches.