Preheat oven to 180°C. Place the pistachios on a baking tray. Bake for 5 minutes or until lightly toasted. Place in a clean tea towel and rub to remove the skins. Set aside to cool slightly.
Meanwhile, stir the sesame seeds, coriander seeds and cumin seeds in a frying pan over medium heat for 3 minutes or until aromatic. Transfer to a plate and set aside to cool slightly.
Place the pistachios and sesame seeds mixture in the bowl of a food processor and process until coarsely chopped. Taste and season with salt and pepper.
To make the chilli mayo, combine the mayonnaise, lime juice and chilli in a small bowl.
Arrange the prawns on a serving platter. Serve with the chilli mayo, dukkah and lemon wedges.