Tip the cubed butter, sugar and flour into the bowl of a food processor.
Attach the lid and pulse the mixture three or four times until it gets to the breadcrumb stage.
Add the egg yolk and pulse to combine until the mixture starts to clump. Add any extra water a few drops at a time.
Turn the processor on full and within a few seconds the mixture should come together into a ball.
Form it into a flat round shape with floured hands.
Wrap in plastic and chill for 30 minutes.
Roll out the pastry to line the tin, making sure that it fits into the bottom edges.
Leave the pastry to hang over the side and prick the pastry base with a fork.
Bake the pastry case blind at 200 C / 400 F / 180 FAN / Gas 6 for 15 minutes or until the pastry has set.
Remove the beans and paper and cook for a further 5 minutes.
Allow to cool.
Carefully cut away any excess pastry with a sharp knife.
Spread over the jam.
Cream the butter and sugar together in an electric mixer until the mixture is light and fluffy.
Add the eggs one by one and beat thoroughly after each addition.
Use a large metal spoon to fold in the breadcrumbs.
Cover the jam with the sponge mixture in an even layer.
Cook in a preheated oven at 160 C / 310 F / 140 FAN / Gas 2.5 for 30 - 40 minutes until set and golden on top.
Leave to cool for 10 minutes in the tin before turning out.