Curry Puffs

Ingredients:

1/2 small onion, finely chopped
150g potatoes, peeled and cut into 1cm cubes
300g lamb mince
1 1/2 teaspoons mild curry powder
1/2 cup chicken stock
1 teaspoon cornflour
2 tablespoons finely chopped mint
4 sheets of frozen-ready rolled puff pastry
salt & pepper to season