Process hamburger bun in food processor until crumbs form. Transfer to a bowl.
Combine oil, garlic, and beans in processor. Pulse about eight times or until a thick paste forms. You may need to scrape down the sides.
Scrape mixture into bowl with breadcrumbs.
Add remaining ingredients and mix with fork.
Coat a large skillet with nonstick cooking spray or a light coating of oil.
With your hands, form bean mixture into four separate patties. Heat skillet over medium-high heat, and then place patties in skillet.
Reduce heat to medium, and cook about four minutes until bottom edges start to brown.
Carefully flip patties over, and top with cheese if desired. Cook about three more minutes.
While patties are cooking, toast buns and prepare desired toppings such as sliced raw onion or chopped sauteed onion; sauteed mushrooms; and sliced tomatoes.
Serve burgers with toppings, and ketchup, mayonnaise, and mustard, if desired.