Cut off a third of each pita and set the pita pockets aside.
Grate the small pita pieces on the fine side of grater, or pulse in food processor, to make 1/2 cup breadcrumbs.
In a large bowl, mix the crumbs, chicken, feta, 1/4 cup mint, salt, pepper and egg until just combined. Shape the mixture into 8 small 3/4-inch-thick burgers.
Heat a 12-inch nonstick skillet over medium heat. Add the burgers and cook until browned on both sides and cooked through, 10 to 12 minutes.
Meanwhile, in a small bowl, combine the yogurt and remaining 1/2 cup mint. To serve, fill each pita with some lettuce, tomatoes, 2 burgers and some yogurt sauce. Make it a Drop 5 Meal by adding: 1/2 cup frozen sweet potato fries, baked. 500 complete meal calories.