In a large bowl, mix together the ground beef, onion soup mix, water, garlic, hot pepper sauce, chili powder, ketchup, mustard and pepper using your hands. Pat into 4 large thick patties. Place them on a broiler pan.
Broil the burgers for about 15 minutes per side, or until well done. Place buns on the broiler pan and toast briefly. Place whole green onions on the broiler pan at the same time, and just toast until limp.
Place burger patties onto the bottom halves of the buns and top each one with a slice of cheese and some avocado slices. Top with the top buns. Serve with green onions.
