Makes about 40 biscuits
200g unsalted butter at room temperature
280g caster sugar
1tsp vanilla extract
400g plain flour
pinch of salt
1/2 tsp cream of tartar
1 sachet egg white powder
1tsp lemon juice
300g icing sugar
A drop of food colouring (optional)
Preheat the oven to 170°C. Beat the butter, sugar & vanilla until pale and fluffy. Mix in the egg.
Add the flour, salt and cream of tartar and gently mix until the dough comes together. Try not to overwork it.
Dust a surface with flour and roll out your dough to about 6mm thick. The thicker you cut it the softer your cookies will be. If you want them thin and crispy go for about 3mm. Space them evenly on a baking tray with at least an inch between them. Bake for about 10 minutes or until the edges just start to turn golden.
Remove from the oven, leave to cool slightly then put them on a cooling rack.
To make the royal icing, place all of the icing ingredients in a bowl and gradually mix in a few tablespoons of water at a time until you have a nice thick drizzling consistency. Whisk for about 5 minutes until thickened. When they are cool completely decorate with the icing using a piping bag, then add sprinkles of your choice!