1) For the Chilli-lime dipping sauce: Combine the yogurt, mayonnaise, grated lime, juice and chili powder in a small bowl and mix well to incorporate. Set aside.
2) For the Popcorn prawns: Place the flour, chili powder, garlic powder and 1/2 tsp of the salt in a shallow bowl and stir with a fork to mix. Place the egg whites in another shallow bowl and beat lightly. Place the cornmeal, remaining 1/4 tsp salt and pepper in a third bowl and stir with a fork to incorporate.
3) Working with a few at a time, toss the prawns in the flour until well coated, shaking off the excess. Then dip the prawns in egg whites, and transfer to the cornmeal mixture and toss to cover all sides. Transfer prawns to a piece of non-stick baking paper repeat with the remaining prawns.
5) Preheat the grill on high. Brush a large baking tray lightly with the oil and heat under the grill for 3 minutes. Remove from the grill and quickly arrange the prawns in a single layer on the tray. Brush lightly with oil. Place prawns under grill and cook until crisp and browned, about 5 minutes. Serve the prawns with dipping sauce.
Per Serving: Calories 210; Total Fat 8 g; (Sat Fat 1 g, Mono Fat 2 g, Poly Fat 1.5 g) ; Protein 15 g; Carb 18 g; Fiber 1 g; Cholesterol 90 mg; Sodium 360 mg