PreparationFor dressing: Whisk Sherry wine vinegar, Dijon mustard, ground cumin, and curry powder to blend in medium bowl. Add olive oil and whisk to blend. (Can be prepared 1 day ahead. Cover and refrigerate. Bring dressing to room temperature and rewhisk before using.) For salad: Whisk yogurt, garam masala, and lemon juice in large bowl to blend. Add chicken breasts; toss to coat. Cover and refrigerate at least 1 hour and up to 1 day, turning occasionally. Prepare barbecue (medium heat). Grill chicken until juices run clear when pierced in thickest part, about 10 minutes per side. Place romaine and baby greens in large salad bowl. Add dressing and toss to coat. Divide salad among 4 plates. Top each with sliced red onion, 1 fresh mint sprig, raita, and grilled chicken. Serve with lime wedges. A spice mixture available at Indian markets and many supermarkets. To substitute, mix 1 1/2 teaspoons ground cumin with 1 1/2 teaspoons ground coriander, 1 teaspoon freshly ground pepper, 1 teaspoon ground cardamom, 1/2 teaspoon ground cloves, and 1/2 teaspoon cinnamon.