In a large bowl, whisk yogurt and tandoori seasoning until blended. Add chicken and turn to coat. Cover and refrigerate at least 30 minutes or overnight, turning occasionally., Meanwhile, in a small bowl, combine slaw ingredients. Refrigerate, covered, until serving. For sauce, combine yogurt, mint, lime juice, garlic, salt and pepper. Refrigerate, covered, until serving., Drain chicken, discarding marinade. In a large cast-iron or other heavy skillet, heat oil over medium heat. Add chicken; cook until a thermometer reads 170°, 5-6 minutes on each side. Spread sauce over toasted bun tops. On each bun bottom, layer lettuce, chicken and slaw. Replace tops.