Chop mushrooms into very small pieces – about the size of diced onion. Heat oil in a large sauté pan, add onions and mushrooms, season with some salt, and cook until they have released their moisture (about 10 minutes).
Add oats to the bowl of a food processor and pulse a couple times. Add half of the beans, the egg, cumin, paprika, chili powder, and salt. Puree until everything comes together – it does not have to be perfectly smooth.
Combine the puree with the rest of the black beans and mushroom mixture in a large bowl and ma6sh together.
Heat oven to 400˚F and line a baking sheet with parchment. Form 6-8 patties and place on parchment – the mixture will probably be quite sticky so use two spoons and form patty right on the parchment.
Bake for 20 minutes, until slightly firm to the touch. Let rest 5-10 minutes while you prep the buns and toppings.
Recipe by Eat Some Wear Some at https://eatsomewearsome.com/black-bean-mushroom-burgers/