Drain and rinse the black beans, then mash them roughly in a mixing bowl with a fork or potato masher, leaving some chunks for texture.
Finely chop half an onion and mince a clove of garlic, then sauté them in a bit of oil in a skillet over medium heat until soft, fragrant, and slightly translucent, about 3 minutes.
Add the sautéed onion and garlic to the mashed beans, then pour in the beaten egg and stir in the oats and cumin until everything is well combined and slightly sticky.
Divide the mixture into four roughly equal portions and shape each into a patty about 1.5 cm thick. Place the patties on a tray or plate and chill them in the refrigerator for 15 minutes to help them hold together better during cooking.
Heat a skillet over medium heat and add a tablespoon of oil. Once shimmering, carefully place the patties in the pan, pressing gently to flatten slightly.
Cook the patties for 4-5 minutes on one side until golden brown and crispy, then flip carefully with a spatula and cook for another 4-5 minutes until the other side is equally golden and the patties are firm.
Remove the burgers from the pan and let them rest for a minute; they should be crispy on the outside and tender inside.
Serve the black bean burgers hot with your favorite buns, toppings, and condiments for a satisfying meal.