Heat the oven to 375°F, spread the beans on a sheet pan and bake for 10 minutes until their skins look dry and split.
Mash three-quarters of the beans in a bowl, leaving the rest whole for texture.
Stir in the panko, egg, red onion, cumin and salt and shape the mixture into 4 firmly packed patties.
Whisk the mayonnaise, chipotle and lime juice together for the sauce.
Coat a nonstick skillet lightly with oil and cook the patties over medium heat for 4 to 5 minutes per side until browned and firm at the edges.
Rest the patties for 2 minutes so the crumbs can set, and toast the buns in the skillet.
Spread chipotle lime sauce on the buns and assemble with lettuce, tomato and one black bean patty.