Scrub and wash the outside of a sweet potato. Use a fork to stab the potato several times and then place it in the microwave and cook for two minutes. Use oven sits to remove from the oven and allow it to cool. After it's cooled, chop into large cubes.
Place the oatmeal and walnuts in a food processor and pulse until a coarse flour is formed.
Add the cubed sweet potatoes, drained black beans, onions, garlic powder, taco seasoning, nutritional yeast flakes, and ground flax seeds. Pulse for a couple of seconds and then use a spatula to push the ingredients back down. Pulse again for several seconds. It's good to leave some texture in the burgers so don't puree it down to a paste, just creating a cohesive mass.
Add the frozen corn and use a spatula to stir it throughout. Let that mixture sit for about 5 minutes.
When you're ready to cook the burgers, turn your oven to 200°F and spray a skillet with vegetable cooking spray. Place the skillet over medium to medium-high heat. Form patties and place them in the heated skillet using a spatula.
Cook patties for about 5 minutes on one side. Sprinkle salt and pepper on the uncooked side of the patties. Flip the patties and cook on the other side until the patties have firmed up and are brown on both sides.
Place the cooked burgers on a baking pan and place that pan in your heated oven or toaster oven. Repeat cooking any remaining veggie patties using the process described above until all the burgers are cooked, allowing each about 10 minutes to stay in the oven before serving.
Serve on toasted buns with dairy-free mayo, pickles, onions, and sliced tomatoes.