How to Make It
Preheat oven to 350°.
Spread half of beans in a single layer on a foil-lined baking sheet. Bake at 350° for 20 minutes. Place toasted beans in a large bowl.
Heat a small saucepan over medium heat. Add 1 teaspoon oil to pan; swirl to coat. Add shallots; sauté 2 minutes or until tender. Add 3 tablespoons quinoa; cook 2 minutes or until toasted, stirring frequently. Add 6 tablespoons water; bring to a boil. Cover, reduce heat, and simmer 10 minutes or until liquid is absorbed.
Combine remaining 2 tablespoons uncooked quinoa, mushrooms, garlic, and remaining (untoasted) beans in a food processor; pulse until coarsely chopped. Add the cooked quinoa mixture, cilantro, serrano, cumin, 1/2 teaspoon salt, chile powder, and egg; pulse until combined. Add mixture to toasted beans; stir well to combine. Divide the mixture into 4 equal portions; shape each portion into a 1/2-inch-thick patty.
Heat a large cast-iron skillet over medium heat. Add remaining 1 tablespoon oil to pan; swirl to coat. Add patties; cook 10 minutes, gently turning once.
Combine chopped avocado, lime juice, tomatillo, and remaining 1/8 teaspoon salt in a small bowl; mash to desired consistency.
Place 1 patty on bottom half of each bun. Top each patty with 1 tomato slice, 1 onion slice, and about 2 tablespoons avocado mixture. Top with top halves of buns.
MyRecipes is working with Let's Move!, the Partnership for a Healthier America, and USDA's MyPlate to give anyone looking for healthier options access to a trove of recipes that will help them create healthy, tasty plates. For more information about creating a healthy plate, visit www.choosemyplate.gov.