1.     Preheat the Oven: Begin by preheating your oven to 450°F (230°C). Cover a rimmed baking sheet with foil to make cleanup easier.

2.     Prepare the Vegetables: Place the halved mushrooms and chopped onion on the prepared baking sheet. Drizzle with 1 tablespoon of olive oil and toss to coat evenly.

3.     Roast the Vegetables: Roast in the preheated oven for 10 minutes. Then, reduce the temperature to 425°F (220°C) and add the rinsed black beans to the pan. Continue to roast for another 5 minutes, or until the mushrooms and onions are browned and the beans are slightly dried on the surface.

4.     Cool the Mixture: Remove the baking sheet from the oven and let the vegetable mixture cool for about 10 minutes.

5.     Blend the Ingredients: Transfer the cooled mixture to a food processor. Add the cooked brown rice and walnuts, pulsing until roughly chopped. Then, add the Worcestershire sauce, ketchup, soy sauce, garlic powder, smoked paprika, chili powder, ½ teaspoon of salt, and ½ teaspoon of pepper. Pulse until just combined. Finally, add the egg and pulse again until mixed.

6.     Form the Patties: Transfer the mixture to a medium bowl and fold in the dry bread crumbs until everything is well combined. Chill the mixture in the refrigerator for about 10 minutes. This helps the patties hold their shape.

7.     Cook the Burgers: Form the mixture into 8 patties, seasoning each one with additional salt and pepper as desired. Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add 4 patties and cook undisturbed for about 4 minutes, or until they are browned and a nice crust forms. Flip the patties and cook for an additional 4 to 5 minutes, topping with Muenster cheese if desired. Repeat the process with the remaining patties.

8.     Serve: Place the cooked patties on toasted hamburger buns and add your favorite toppings.