In a mixing bowl, add yogurt, paprika,chilli powder, turmeric powder,ajwain seeds, nigella seeds,ginger and garlic paste, salt, oil and the gram flour paste; mix well.
Now add in the prawns.
Leave refrigerated for about 20 minutes and bring to room temperature before grilling in a tandoor until cooked to required doneness.
To cook in an oven, pre-heat to 200 c / gas mark 6.To grill, place the marinated prawns on a cooking rack (with a drip tray below) and grill in the oven for 4 minutes, turn the pieces and grill for 3-4 minutes or until done.
Remove and set aside to cool.Serve hot,garnish with chives, melted butter and chaat masala; accompanied with baby leaf salad.