Place beans in a food processor; cover and process until blended. Transfer to a large bowl. Add the bread crumbs, tomato, jalapeno, egg, cilantro and garlic. Mix until combined. Shape into four patties.
In a large nonstick skillet, cook patties in oil in batches over medium heat for 4-6 minutes on each side or until lightly browned. Serve on buns. Top with sour cream and guacamole if desired.