Pre-heat the oven to 180°C.

Sieve all the dry ingredients together. Rub the butter into the mixture until it resembles breadcrumbs.

Beat the egg, water & vanilla essence together and add to the flour/butter mixture. Mix until they have formed a tight dough. Reserve about a quarter of the dough and store in the freezer.

Press the remaining dough into a greased baking sheet and bake for 10 minutes.

Remove from the oven and use a pastry brush to spread on the desired amount of apricot jam, then grate the reserved frozen dough over the cooked dough, taking care not to spread it too thickly.

Put the tray back in the oven for a further 20 minutes until golden. Remove from the oven, allow to cool and cut into squares.