Cut the steamed potatoes into 4 to 5 pieces each and add them to a large bowl. Mash the sweet potatoes until smooth.

Pat dry the black beans with paper towels to remove any excess moisture. Add them to the mixing bowl with sweet potatoes. Mash only about half of them so you have some whole beans. Not mashing them all gives a nice texture and bite to the burgers.

Add the finely diced onions, ginger paste, garlic paste, minced green chili, turmeric, salt, and garam masala. Mix everything together thoroughly with a rubber spatula.

Gradually mix in the oat flour, a little bit at a time, until the mixture is firm enough to form patties. The oat flour will absorb excess moisture and help form the patties. If making ahead, you can keep this mixture in the fridge for up to 24 hours.

Press down the mixture in the bowl so it's evenly flattened. Using a rubber spatula, divide the mixture into 6 equal parts. Scoop up each part and shape into a 4-inch patty. Lightly oil your hands if needed. Place the patties onto a parchment paper-lined tray. Repeat with the remaining mixture.

Heat a non-stick pan or griddle over medium heat. Add 2 teaspoons of oil and gently pan-fry 2 to 4 patties at a time. Allow burgers to cook on one side for 4 to 5 minutes on low-medium heat before flipping over. Cook the other side for 4 to 5 minutes or until both sides are golden brown and crisp.