In a large mixing bowl, mash the black beans with a fork or potato masher until they form a chunky paste.
Add the cooked quinoa, mushrooms, onions, garlic,tomato paste, soy sauce, smoked paprika, cumin, salt, and black pepper to the bowl. Thoroughly blend the ingredients together for a proper combination.
Gradually add the breadcrumbs to the mixture until it reaches a consistency that allows you to form patties. The mixture should hold together without being too dry or too sticky.
Partition the mixture into uniform portions and mold each portion into a patty shape. The number of patties you'll obtain will vary, typically ranging from 4 to 6, depending on your preferred size.
Heat a drizzle of oil in a non-stick skillet or grill pan over medium heat. Cook the patties for about 4-5 minutes on each side until they are browned and heated through.
Toast the burger buns lightly if desired.
Assemble your plant burgers by placing the cooked patties on the buns and adding your favourite toppings such as lettuce, tomato,onion, avocado, or any condiments of your choice.
Serve the plant burgers warm and enjoy!