Corn and two-bean burgers with Chipotle Ketchup

Ingredients

Burger:
2 tablespoons olive oil
1 (15-ounce) can kidney beans, rinsed and drained
1 (15-ounce) can black beans, rinsed and drained
1/3 cup dry breadcrumbs
1/4 cup canned whole-kernel yellow corn, drained
1/4 cup prechopped onion
1 large egg

Ketchup:
1/3 cup ketchup
1 teaspoon honey
1 teaspoon lime juice
1/2 teaspoon chipotle chile powder
1/2 teaspoon ground cumin

Remaining ingredients:
4 (2-ounce) Kaiser rolls or hamburger buns
4 lettuce leaves (optional)
4 (1/4-inch-thick) slices tomato (optional)

Preparation

To prepare burgers, heat oil in a large nonstick skillet over medium-high heat.
Combine kidney beans and black beans in a large bowl; partially mash with a fork. Add breadcrumbs, corn, onion, and egg; stir until well blended. Form bean mixture into 4 (1/2-inch-thick) patties. Add patties to pan; cook 4 minutes on each side or until crisp and beginning to brown.
To prepare ketchup, combine ketchup, honey, lime juice, chile powder, and cumin, stirring with a whisk.
Spread 1 tablespoon ketchup on bottom half of each bun; top each serving with a patty, 1 lettuce leaf and 1 tomato slice (if desired), and top half of bun.