Make a double batch, for now and later. These flavorful burgers can be frozen up to two months; thaw patties overnight in the refrigerator, and broil.
Preheat broiler, with rack set 4 inches from heat. In a medium bowl, mix together bread pieces, turkey, sour cream, 3 tablespoons chutney, 1 tablespoon mustard, chili powder, and 1 teaspoon coarse salt.
Shape mixture into four 5-inch round patties. Broil on a rimmed baking sheet until firm and cooked through, 4 to 5 minutes per side.
Meanwhile, lightly toast remaining 4 slices bread; transfer to serving plates. Top each slice with lettuce, burger, and tomato. Stir together remaining tablespoon chutney and mustard; serve alongside burgers.
For single servings: Delicious right away, ideal to freeze. Wrap uncooked patties individually, and defrost just the number of burgers you need.