Form meat into four oval patties, about half pound each. Season patties generously with salt and pepper. Grill until desired doneness; remove from grill and let rest. Toast bun only on the cut side until light brown. Smear about 2 tbsp of mayo on the top and bottom bun. Place cooked patties on the bottom bun then add two pieces of bacon. Sprinkle 1 oz of cheese, 3 tablespoon onion jam and arugula.