Very simple, very cheap, and well-balanced in protein with the grain/legumes. Probably tastes better with kidney beans, black beans, or combination, but I got the pintos because they come in the biggest bag.
Soak a pound of whichever beans overnight, then change the water, add the onions and cookem for an hour. Towards the end, pour off excess water. Mix the chili powder & vegan sugar with a little water and add slurry to beans. Load up the buns and gobble down. Good for 8-10 sandwiches.
Maybe use molasses instead of brown vegan sugar to make the stuff more cohesive? Could also try adding nuts/barley/etc for texture.