Preheat oven to 200C. Sift the flour, salt and sugar into a bowl and cut in the butter until it resembles fine breadcrumbs. Add the beaten egg and combine until it forms a dough. Chill in the fridge for 30 minutes.
Roll pastry out on a lightly floured surface quite thinly and cut into rounds. Place the rounds in a tartlet tray (bun tray).
Put a maximum of 1 1/2 tsp of jam of your choice into the tart cases. This pastry shrinks so do not fill to the brim. And put in the oven for approximately 15 minutes.
Remove form the oven and remove from the tartlet tray immediately and place on a wire rack. Allow to cool before eating as the jam will be exceedingly hot.