In a large bowl, add black beans, rice, corn, seasonings, and egg.
Use a potato masher to combine all ingredients until thoroughly mixed together.
Add the bread crumbs and mix to combine.
Take 1/4 of the mixture and shape it into a patty using your hands. Repeat with the remaining mixture to create four patties.
Heat a small amount of oil over medium heat.
Once heated, add the patties and cook for 4-5 minutes on each side.
Serve with pretzel buns, lettuce, tomato, avocado, red onion, ketchup, and mustard.