Heat grill to medium. Brush eggplant with 3 Tbspoil, then season withcoriander, cayenne, and1⁄4 tsp salt. Grill until tender,10 to 12 minutes.Meanwhile, in a medium bowl, whisk together lemon juice, vinegar, remainingTbsp oil, and 1⁄2 tsp salt;fold in tomatoes, chiles,and mint.Arrange eggplant on a large platter; top withtomato salad. Whisk togetheryogurt and milk and drizzleover vegetables. Sprinklewith mint leaves if desired.