In a large bowl, combine the beans, onion, garlic, chipotles, adobo sauce, tamari, balsamic, cumin, salt, and pepper. Use a potato masher to mash until the mixture holds together but still has some visible chunks of black beans. Add the egg and use a spatula to fold until combined. Then, fold in the panko.
Use your hands to form the mixture into 6 patties. The mixture should be cohesive and a little wet. If it’s too wet to handle, chill in the fridge for 20 minutes to firm up or mash your beans a little bit more.
Heat a cast-iron skillet over medium heat. Brush with a little oil and cook the burgers for about 5 minutes per side, until charred on both sides, turning the heat down as necessary. The exact timing will depend on the heat of your stove and cookware.
Alternatively, preheat an outdoor grill to 400°F. Lightly brush the patties with olive oil, spray the grill grates, and grill for 8 minutes on the first side and 4 minutes on the second side.
Serve with hamburger buns and desired fixings.