Preparation In a bowl, combine beans, corn, bell pepper, breadcrumbs, cilantro, egg whites, chipotle, oregano and cumin. Form bean mixture into four 3/4-inch-thick patties. In a large nonstick skillet, heat 1 tablespoon oil over medium-high heat. Cook patties, turning once, until browned, 5 minutes per side; remove from pan. In same skillet, sauté spinach in remaining 1 teaspoon oil over medium-high heat until wilted, 3 minutes; season with nutmeg and salt and freshly ground black pepper. In another bowl, mix avocado with sour cream and juice. Place 1/4 of cooked spinach on bottom of each bun, then 1 burger and 1/4 avocado mixture. Top with other bun half. Per serving: 400 calories, 14 g fat, 4 g saturated fat, 58 g carbohydrate, 12 g fiber, 18 g proteinNutritional analysis provided by Self