Preheat the oven to 200°C. Line a baking tray with baking paper
De-stem the mushrooms and place them on the tray. Drizzle olive or coconut oil over the mushrooms, season with a little salt and pepper and bake in the oven for 15minutes, or until the mushrooms are tender. They will shrink in size a little
When cooked, place the mushrooms stem side down on paper towel to remove excess moisture. Allow to cool
While the mushrooms are cooking get the rest of your vegetables ready. Slice the tomatoes, avocado, red onion and cheese. Wash the lettuce and dry with paper towel
To make the patties combine beef mince, onion, egg and herbs together in a bowl. Shape mixture into 3 patties (ensure they are not larger than the mushrooms). Heat olive or coconut oil in a large frying pan over medium heat. Add patties. Cook for 4-5 minutes each side, or until cooked through
When all of the ingredients are ready, build your burger. Enjoy!