Start by bringing a large pot of water to a boil. Add the peeled and chopped sweet potato and cook until tender, about 15-20 minutes. Drain and let cool slightly.
In a large mixing bowl, combine the cooked sweet potato, half of the black beans, red onion, rolled oats, ground flax seed, garlic powder, ground cumin, and kosher salt. Use a fork or potato masher to mash the mixture until well combined but still a bit chunky.
Finely chop the chipotle peppers and add them along with the tablespoon of adobo sauce to the sweet potato mixture. Stir in the remaining black beans, ensuring that they remain mostly whole for added texture.
Using your hands, form the mixture into patties of your desired size. This recipe should make about 6-8 burgers, depending on how large you make them.
Heat the avocado oil in a skillet over medium heat. Once hot, add the patties and cook for about 5-6 minutes on each side, or until they are golden brown and heated through. If baking, preheat your oven to 375°F (190°C) and bake for about 25-30 minutes, flipping halfway through.
Toast your burger buns lightly. Spread some chipotle mayo on the bottom half, add the sweet potato black bean patty, and top with red onion, lettuce, and avocado. Finish with the top bun and enjoy!
