Messy Burger

Ingredients

• 1 large onion (sliced into thin half rings)
• 1 pound of fresh mushrooms (sliced)
• 1 tablespoon of olive or avocado oil
• 1 pound ground beef
• 4 slices of cheese
• 1 tablespoon of salt (or preferred seasoning)
• 4 burger buns (try brioche for extra flavor)
• Ketchup
• Mayonnaise