Preheat your oven to 350ºF. Spread the beans in a single layer on a baking sheet and leave in the oven for 10-15 minutes or until the beans begin to open. Let cool. While the beans are in the oven, sprinkle salt and pepper on the shiitake mushroom slices and cook in a little olive oil in a pan over medium heat. Cook on both sides until golden. They won't get crisp like bacon but will have a nice umami flavor.
In a bowl combine all the ingredients from the beans to the 2-3 tablespoons of mayo. Use your hands to mix the ingredients together. The mixture shouldn't be too dry and too moist. There should be enough moisture for the ingredients to hold together. If it looks too wet, add another tablespoon or two of breadcrumbs or oats. Form into six patties (or less or more depending on the size patties you want). Remember that unlike traditional beef patties, these bean burgers won't shrink when you fry them.
Heat one tablespoon of olive oil in a skillet over medium heat. Cook each burger patty for about four minutes on each side or when you start to see some golden sections on the patties.
If using cheese (vegan or regular), add the slices on the flipped burgers during the last minute or two of cooking time. Assemble your burgers and enjoy.
Black Beans: Instead of canned beans for this batch I used dried beans I cooked myself, about 20 ounces.