Make the pastry cases ahead of time and use everyday ingredients to create a tasty party nibble in minutes.
For the pastry
For the filling
For the pastry pulse the flour and butter in a food processor until the mixture resembles fine breadcrumbs. With the motor running, add the beaten egg and blend until the mixture starts to come together in a ball. Shape the dough into a ball and flatten slightly.
Roll the pastry out on a floured work surface, and using a 7.5cm/3in cutter, cut out 12 rounds. Use them to line a 12-hole muffin tin.
Prick the base of the pastry with a fork, and freeze for one hour.
Pre-heat the oven to 200C/400F/Gas 6.
Bake the pastry cases for 15-18 minutes, or until lightly browned and cooked through.
Remove from the oven and transfer to a wire rack to cool.
For the filling, coat the apple slices in lemon juice to prevent them from browning.
Spoon a little mayonnaise into each pastry case and arrange small pieces of apple, cheese, celery, spring onion and tomato on top.
Add half a teaspoon of pickle or chutney and garnish with a few celery leaves.
Once cool, the pastry cases can be stored in an airtight container for up to three days.