01 - Combine ground flaxseed and water in a small bowl and allow to thicken for 5 minutes.
02 - In a large mixing bowl, mash black beans until mostly smooth with some texture remaining.
03 - Add oats, breadcrumbs, red onion, garlic, flax egg, tomato paste, smoked paprika, cumin, chili powder, salt, and pepper to beans. Mix thoroughly until uniform.
04 - Divide mixture into four equal portions and shape each into a firm patty.
05 - Heat olive oil in skillet over medium heat and cook patties for 5 to 6 minutes per side until browned and heated through.
06 - In a small bowl, combine vegan mayonnaise, chopped chipotle peppers, adobo sauce, lime juice, and salt. Stir and adjust seasoning as needed.
07 - Optionally toast the burger buns before assembling.
08 - Spread chipotle mayo on buns, add black bean patty, then layer with lettuce, tomato, red onion, and pickles. Serve immediately.