Southwest Meatball Supper

• 1 onion
• 1 egg
• 1 head iceberg lettuce
• 1 ripe avocado
• 450 gr beef (lean ground)
• 450 ml mild taco sauce
• 55 gr fine dry bread crumbs
• 45 ml vegetable oil
• 32 gr coarsely monterey jack cheese (grated)
• 8 gr chili powder