Cream the butter and sugar until smooth about 5 minutes. Carefully beat in the egg white. Sieve the flour into the mixture and beat into a smooth dough. (It feels like plasticine that you’ve been holding for a long time).
Line and grease a baking tray. Spoon the dough into a piping bag fitted with a large nozzle. Squeeze out the dough into rosettes, spacing them well apart on the baking tray.
Put a drop of jam in the centre of each biscuit. Use a brightly coloured jam that will contrast with the colour of the biscuit – strawberry, raspberry, red cherry and apricot are all suitable.