1. Preheat grill to 350° to 400° (medium-high) heat. Process first 4 ingredients and 1/4 cup water in a blender until smooth. Add mint and next 3 ingredients, and process until smooth, stopping to scrape down sides as needed.
2. Rub 1/2 cup cilantro mixture over chicken; cover and chill 10 minutes. Reserve 1/2 cup cilantro mixture for Grilled Chicken Naan Pizza and 1/2 cup to serve with chicken.
3. Grill chicken, covered with grill lid, 5 to 6 minutes on each side or until done. Remove from grill, and let stand 5 minutes.
4. Meanwhile, grill tomato halves 3 to 5 minutes or just until they begin to blister. Sprinkle with salt and pepper, drizzle with desired amount of olive oil, and top with chopped fresh herbs. Grill naan 1 to 2 minutes on each side or just until puffy and soft.
5. Reserve 6 chicken thighs and 4 tomato halves for Grilled Chicken Naan Pizza. Serve remaining chicken and tomatoes with grilled naan bread and reserved 1/2 cup cilantro mixture.
LEFTOVER DINNER: Grilled Chicken Naan Pizza: Preheat oven to 450°. Thinly slice 6 Grilled Spicy Cilantro Chicken thighs. Place 2 naan breads on a parchment paper-lined baking sheet; spread each with 1 Tbsp. reserved cilantro mixture; layer each with 1/2 cup sliced chicken, 4 reserved plum tomato halves, and 4 fresh mozzarella cheese slices. Bake 7 to 8 minutes or until cheese melts. Top with arugula. Serve with remaining cilantro mixture. Makes 4 servings.