01 - In a small bowl, combine ground flaxseed and water. Set aside for 5 minutes to thicken.
02 - Pulse rolled oats in a food processor until a coarse meal forms.
03 - Add black beans, red onion, cilantro, garlic, tomato paste, cumin, smoked paprika, salt, pepper, and flax egg to the food processor. Pulse until mixture is combined but retains some texture.
04 - Shape the mixture into four equal-sized patties.
05 - Heat olive oil in a large skillet over medium heat. Cook patties for 4 to 5 minutes per side until golden and heated through.
06 - In a small bowl, combine vegan mayo, minced chipotle peppers, adobo sauce, lime juice, and salt. Mix until smooth.
07 - Toast the burger buns if desired.
08 - Spread chipotle mayo on each bun, then add lettuce, tomato slices, red onion slices, black bean patty, and vegan cheese if using. Top with remaining bun halves.
09 - Serve immediately while warm.