1 Place butter, crystals, sugar and essence in the small bowl of an electric mixer. Beat until light and fluffy. Beat in egg until just combined. Transfer to a bowl.

2 Add combined sifted flours in two batches. Stir until mixture forms a soft dough. Refrigerate for 10 minutes.

3 Roll tablespoons of mixture into balls. Place, about 5cm apart, on three oven trays lined with baking paper. Press to flatten slightly.

4 Cook, one tray at a time, in a moderate oven (180C) for about 5 minutes, or until lightly browned. Stand for 5 minutes, then transfer to a wire rack to cool.

5 To make coloured icing, place egg white in a small bowl. Stir in sifted icing sugar in two batches. Divide mixture between two small bowls. Tint one yellow and the other blue with food colouring.

6 Spoon teaspoons of icing onto biscuits. Decorate with a jelly bean. Stand on a wire rack until set.