1. Make the pastry by cutting the butter into cubes and adding to the flour in a bowl, then rubbing it in with your fingers until the texture resembles breadcrumbs. Add just sufficient cold water for the mixture to amalgamate to a firm dough.
2. Roll the dough into a ball, wrap it in cling film and chill it in the fridge for 10 minutes.
3. Pre-heat the oven to 200°C (400°F). Roll out the pastry to line a 10-inch flan dish and prick the bottom several times with a fork. Blind bake the pastry case by placing it in the hot oven for 5 minutes until just firm to the touch.
4. Wash the mirabelles, cut them in half and remove the stones. Place them skin side down in the pastry case. Sprinkle the fruit with two tablespoons of the sugar.
5. Beat the rest of the sugar with the egg. Stir in the flour and mix until the paste is completely smooth. Then stir in the milk or cream, melted butter, and eau de vie.
6. Pour the batter mixture over the plums and bake at 200°C (400°F) for 45 minutes.

Serves 6-8.