Preheat the oven to 200C/390F/Gas 6.
Heat the oil in a wok or frying pan. Add the onions and fry until they start to soften. Add the ginger and beef and fry until browned.
Add the curry powder, soy sauce, water, sugar, salt, potatoes and peas. Cook for ten minutes, stirring occasionally, reducing the liquid until the mixture is moist but not sloppy. Stir in coriander and leave to cool.
Roll out the pastry and cut out 10cm/4in rounds of. Place one tablespoon of the curry mixture in the middle.
Fold the pastry over to form a half circle, pressing the edges together with your fingertips or crimping with a fork.
Brush with a little beaten egg and bake for 20 minutes, or until glazed and golden.