01 - If using flaxseed, combine ground flaxseed with 3 tablespoons water in a small bowl. Let the mixture rest for 5 minutes until it thickens into a gel-like consistency.
02 - Heat 1 tablespoon olive oil in a skillet over medium heat. Add the chopped onion, grated carrot, diced bell pepper, and minced garlic. Cook for 4 to 5 minutes until softened. Fold in the chopped spinach and continue cooking until wilted. Remove the skillet from heat and set aside.
03 - Transfer the drained black beans to a large mixing bowl. Using a fork or potato masher, partially mash the beans while leaving some texture intact for a hearty bite.
04 - Add the sautéed vegetables, rolled oats, breadcrumbs, tomato paste, smoked paprika, ground cumin, salt, black pepper, and the prepared flax egg (or regular egg) to the mashed beans. Stir thoroughly until all ingredients are evenly distributed.
05 - Divide the mixture into 4 equal portions. Shape each portion into a firm patty approximately 3/4 inch thick, pressing firmly to ensure they hold together during cooking.
06 - Heat the remaining 1 tablespoon olive oil in the skillet over medium heat. Carefully place the patties in the pan and cook for 4 to 5 minutes per side until golden brown and heated through.
07 - Serve the patties on toasted buns with your preferred toppings such as crisp lettuce, sliced tomato, avocado, and pickles.