1. Sift the flour, icing sugar and cocoa powder into a mixing bowl. Rub or cut in the butter until the mixture resembles fine breadcrumbs.
2. Mix the eggs with the vanilla essence. Add to the dry ingredients and mix to a dough with a round-bladed knife.
3. Knead the dough on a lightly floured surface until smooth. Form into a ball, then wrap in clear film (plastic wrap) and chill for 20 minutes before using.