Mold 1/4 pound of ground beef into ball and flatten out to make an oval patty, about the size of a standard coffee can. Do the same with the remaining ground beef. Place mushrooms and onions in center of one patty. Place the other patty on top and mold into one patty. Mix salt, pepper and garlic together and rub them on both sides of the patty.
Place burgers on grill. Baste with BBQ sauce each time after first flip, this allows seasoning to cook in. Cook to 155°. Top with cheese—Jack's the best—and enjoy!