1.In a large frying pan, heat the oil on high (or use a char-grill pan). Cook chicken, for 4-5 minutes on each side until cooked through. Set aside, covered with foil, for 5 minutes. When cooked, slice thinly.
2.Using the same pan, cook the prawns, turning, for 2-3 minutes until they change colour and are cooked through.
3.Make dressing: In a jug, whisk all the ingredients together.
4.Arrange lettuces on a platter. In a large bowl, combine chicken and prawns with mango, mint, cucumber, capsicum and onion. Drizzle over half the dressing. Toss to combine.
5.Sprinkle with nuts to serve. Drizzle with the remaining dressing and lime wedges.
The soft green of butter lettuce and the red-purple and green leaves of the mignonette complement each other beautifully. Never dress these lettuces until ready to serve to prevent them from going soggy. For a Thai version of this salad, replace the ripe mango with finely shredded green mango. It has a firmer, crunchier texture and slightly sour flavour. Replace palm sugar with brown sugar if you have none on hand.