If grilling, preheat an outdoor grill for high heat, and lightly oil a sheet of aluminum foil. If baking, preheat oven to 375 degrees F (190 degrees C), and lightly oil a baking sheet.

In a medium bowl, mash black beans with a fork until thick and pasty.

In a food processor, finely chop the onion and garlic. Then stir into mashed beans.

In a small bowl, stir together egg, chili powder, and cumin.

Stir the egg mixture into the mashed beans. Mix in bread crumbs until the mixture is sticky and holds together. Divide mixture into four patties.

If grilling, place patties on foil, and grill about 8 minutes on each side. If baking, place patties on baking sheet, and bake about 10 minutes on each side.

Serve on buns and top with lettuce, tomatoes, and ketchup or as desired.