Add peppers, onions and mushrooms to a food processor and pulse until roughly chopped and around the same size
Sauté the vegetable mixture in a pan over medium heat until most of the moisture has cooked out
Remove from pan and set aside
In a large bowl, add black beans, cooked veggies, chickpea flour and ketchup
Mash and mix until all combined and mixture forms a patty
Lay down a layer of thinly sliced onions and pan fry until crispy and cooked through
Melt cheese over top by adding a bit of water to steam and cover until melted
For burger sauce, add all ingredients to a small bowl and mix
Stack patties and quickly toast on a reversed burger bun with pickle and other toppings
