Heat the oil in a high-sided, heavy-based pan. Add the cumin seeds then immediately add the onion and salt. Fry until brown. Add garlic and ginger, fry briefly then add the ground spices. Immediately add the pureed tomatoes. Reduce until the oil has separated from the masala. Add the yoghurt a spoonful at a time, stirring well between each addition. Add the chicken and the cream, stir to combine the remove from the heat to cool. Lay a circle of puff pastry in the base of a muffin tin. Fill with the curry, brush with egg wash then top with a (slightly smaller) circle of pastry. Brush the top with egg and bake for 25 minutes at 190°C.