Really Awesome Black Bean Burgers Recipe

Name: Really Awesome Black Bean Burgers Recipe
Cuisine: American
Ingredients: 2 (15-ounce) cans black beans, rinsed and drained; 4 tablespoons vegetable oil, divided; 1 medium onion, finely chopped; 1 large poblano pepper, finely chopped; 3 medium cloves garlic, minced; 1 chipotle chile in adobo sauce, finely chopped, plus 1 teaspoon sauce; 3/4 cup roasted cashews; 1/2 cup finely crumbled feta or cotija cheese; 3/4 cup panko bread crumbs; 1 large egg; 2 tablespoons mayonnaise; Kosher salt and freshly ground black pepper; 6 cheese slices; 6 to 8 hearty hamburger buns, toasted; Condiments as desired, such as chipotle mayonnaise, ketchup, mustard, or mayonnaise; Toppings as desired, such as shredded lettuce, sliced onions, and pickles