01 - In a small bowl, combine ground flaxseed with water and let rest for 5 minutes until a gel forms. Skip this step if using a regular egg.
02 - Heat 1 tbsp olive oil in a skillet over medium heat. Add onion, carrot, bell pepper, and garlic; cook for 4–5 minutes until softened. Stir in spinach and cook until wilted. Remove from heat and set aside.
03 - In a large bowl, mash the drained black beans using a fork or potato masher, leaving some chunks for texture.
04 - Add sautéed vegetables, oats, breadcrumbs, tomato paste, smoked paprika, cumin, salt, pepper, and the flax egg (or regular egg) to the mashed beans. Mix thoroughly until evenly combined.
05 - Divide the mixture into 4 equal portions and shape into uniform patties.
06 - Heat the remaining olive oil in the skillet over medium heat. Cook patties for 4–5 minutes per side until golden brown and cooked through.
07 - Serve on toasted buns with desired toppings such as lettuce, tomato, avocado, and pickles.