These ginger biscuits provide the perfect opportunity for honing your icing skills. Use the templates included at the end of the recipe to guide you.
Beat the butter, sugar and molasses in a bowl until fluffy. Little by little, add the egg, beating well between each addition. (You can do this in a stand mixer fitted with the beater attachment, if you like.)
Sift together all the remaining ingredients into a bowl. Stir them into the butter mixture.
Place the dough on 1 sheet of baking paper. Place the other sheet on top and press the dough to make a flat layer. Chill for 1 hour, until firm.
Heat the oven to 190°C/170°C fan/375°F/Gas 5.
On a lightly floured work surface, roll out the dough to 5mm thick. Use the cutters to make 6 square and 6 oval biscuits, re-rolling the trimmings as necessary. Place the biscuits on the baking sheets. Chill until firm.
Bake in the middle of the oven for 8–12 minutes, or until the edges of the biscuits are lightly browned. Cool for 1 minute, then transfer to a wire rack to cool completely.
For the royal icing, mix the egg white with 3 tablespoons of the icing sugar in a large bowl and add the lemon juice.
Gradually, add the remaining icing sugar and mix thoroughly until the icing holds its shape. Do not over-beat or bubbles will form.
Divide the icing into 3 separate bowls. Leave 2 bowls white and divide the third bowl of icing between 4 small bowls for decorating the biscuits. Colour 1 portion blue, 1 yellow, 1 green and 1 red.
Drop by drop, add water to the small portions of icing and mix to a piping consistency. Spoon these into the 4 small piping bags fitted with number 1 writing nozzles.
Drop by drop add water to one of the bowls of white icing and mix to a piping consistency. Spoon into the medium piping bag fitted with a No. 1 writing nozzle.
Add water drop by drop to the remaining bowl of white icing and mix to a flooding consistency. Spoon into the medium piping bag fitted with a No. 3 writing nozzle.
Decorate the biscuits according to the templates provided, loosening or thickening the icings with water or icing sugar to the correct consistency.