Mix flour, sugar and salt.
Add cold butter in small pieces and crumble briefly.
Add the egg and quickly knead into a shortcrust pastry.
Wrap the dough in cling film and leave to rest in the fridge for about 1 hour.
Melt the butter.
Mix flour, sugar and cinnamon.
Add the melted butter to the flour and sugar mixture and mix with a fork to form small crumbles.
Roll out the dough on a floured surface.
Cut out Christmas trees (or other shapes) and place on a baking tray with baking paper.
Put a blob of jam on top and sprinkle with crumble.
Bake in preheated oven at 175° C for about 11 minutes.
When cool, store in a biscuit tin.