Mash black beans in a large bowl with a fork until thick and pasty; set aside
In a food processor, chop bell pepper, onion, mushroom, and garlic. Mix with mashed black beans. Blend rice and cheese, then stir into bean mixture until combined
Whisk together the Tahini, chili powder, cumin, salt, and hot sauce. Stir the mixture into the black bean mixture. Stir in the breadcrumbs as needed until the mixture is sticky and holds together. Divide into patties
Brown patties in a skillet or on an outdoor grill until completely heated through, about 8 minutes per side. At the same time, grill the sweet onion until soft and nice grill lines appear
Meanwhile, toast Kaiser bun and prepare burger toppings
Spread vegan mayo on both sides of the bun, then set lettuce and tomatoes on the bottom bun
Add the vegetarian patty, then top it with pickled beets, grilled onion, pico and sliced avocado
