Thinly slice chicken on an angle. Combine paste and yoghurt in a snap-lock bag. Add chicken, seal bag and rub well to coat. Chill for 20 minutes.
Meanwhile, for the salad, soak currants in boiling water for 5 minutes. Combine carrot, onion and coconut in a bowl. Heat oil in a small pan. Add mustard seeds and when they begin to pop, remove from heat. When popping stops, pour hot oil over carrot mixture and toss. Drain currants; toss into salad with coriander.
For the raita, combine all ingredients.
Heat a chargrill over medium heat. Cook chicken for 2 minutes each side or until cooked through. Pile salad, chicken, cucumber and raita on bun bases, then finish with bun tops.