Process pinto beans, onion, brown rice, almonds, cashews, mushrooms, black olives, and garlic in batches in a food processor until completely chopped; transfer to a large mixing bowl.
Mix Parmesan cheese, egg, flaxseed, vegetable bouillon, and Worcestershire sauce into the bean mixture. Cover bowl with plastic wrap and refrigerate for 1 hour.
Preheat oven to 375 degrees F (190 degrees C).
Form bean mixture into 12 patties and arrange onto a non-stick baking sheet.
Bake burgers in preheated oven for 10 minutes, turn, and continue baking until cooked through, about 10 minutes more.
Heat a skillet over medium heat. Cook burgers in hot skillet until browned, 3 to 5 minutes per side.
