100g icing sugar
2 egg yolks
1/2 tsp vanilla essence
1/4 tsp salt
Beat butter and sugar till light and fluffy. Add egg yolks and vanilla essence. Blend in sifted flour and mix well.
Leave aside for 30 minutes, then put mixture into a piping bag. Use a star nozzle and pipe out with short, firm strokes.
Bake biscuits in a preheated oven at 170 ºC for 12 to 15 minutes.