1. Heat a large nonstick skillet over medium-high heat. Add oil; swirl to coat. Add apple, celery, and onion; sauté 5 minutes or until tender. Remove from heat, and cool completely.
2. Grate rind and squeeze juice from lemon to measure 2 teaspoons rind and 1 tablespoon juice. Combine apple mixture, lemon rind, lemon juice, and turkey. Sprinkle with salt and pepper. Add egg; mix gently just until combined. Add hot pepper sauce, if desired. Shape into 6 (1/2-inch-thick) patties. Cover and refrigerate 2 hours or until thoroughly chilled.
3. Preheat grill to high heat. Place patties on grill rack coated with cooking spray. Grill 5 minutes on each side or until done. Place buns, cut side down, on grill rack. Grill 1 minute or until toasted.
4. Combine yogurt and chutney. Place patties on bottom halves of buns; top each patty with 1/4 cup spinach and about 4 teaspoons sauce. Cover with top halves of buns.
Kids Can Help: With clean hands, kids can mix the ingredients into the ground turkey, and then shape the patties.