Before starting this recipe, you need to soak the dried chickpeas in cold water for at least 24 hours.
Preheat your oven to 350°F. Line a large baking sheet with foil, and spread the black beans in a single layer. Roast the beans for 30-35 minutes until they are mostly dried out and beginning to blister.
Heat 2 tablespoons of oil in a large nonstick pan. Add the onions and poblano peppers and cook for 4-5 minutes until soft. Add the garlic, chipotle peppers, and adobo sauce, and cook for another 2 minutes. Transfer to a large bowl with the cashews and cilantro.
Add the black beans and feta to a food processor and blend until well combined (about 10-15 short pulses). The beans should be no larger than ⅓ inch. Transfer to the onion/poblano mixture.
Add the mayonnaise, ½ cup breadcrumbs, egg, salt, and black pepper to the onion/poblano mixture. Use your hands to form six patties (about ½ cup each) and place them on a parchment-lined sheet.
Place the rehydrated chickpeas in a food processor and blend until fine, about 5 long pulses. Transfer to a shallow bowl and mix with ½ cup breadcrumbs.
Whisk the eggs in a flat container. Dip each patty in the egg wash and gently press into the chickpea mixture. Make sure to apply only a thin layer of chickpeas (about 1/16 inch thick). Repeat for all patties.
Heat 1 inch of oil to 350°F. Fry two patties at a time for 4-5 minutes until golden brown. Transfer to a wire rack to drain excess oil.
At this point, you can assemble the burgers. The way I like to do it is by toasting both buns, spreading chipotle sauce on the top and bottom buns, and then adding dill pickles, minced onions, cheese, and lettuce.