One sesame seed bun from the supermarket grocery or your local bakery. It needs to be a fresh bun that's big and covered in tasty sesame seeds.
Layer the bottom with rinsed canned black beans. While buying dried beans may seem more economical, the amount of cooking required negates any savings you might reap. Lentils are the exception. Since lentils only take 20 minutes to cook, the dried kind really do save you money. Anyway, canned lentils are rare in the first place, because of that. Although I did see a can in the market the other day. Food is always evolving.
So you layer the bottom of your fresh sesame seed bun with a small bunch of black beans. About 2 tablespoons worth for an average size bun. Sprinkle beans generously with nutritional yeast flakes. About 1 tablespoon worth. A few grinds of black pepper. Then layer with half a kosher pickle spear worth of slices. I like Mount Olive zesty garlic spears. But whatever you prefer. The acidic juice from the pickles mixes with the yeast to make a great dressing. Then sprinkle with imitation bacon bits. Great crunch and good flavor. Finish with some raw white onion slices. A truly delicious sandwich if ever there was one.
You've got to try it. Whether you are vegetarian, vegan or otherwise culinarily inclined. It's really, really good sammie regardless.