Step 1 of 5

In a large bowl, mix butter and icing sugar. Add 2 spoons of vanilla extract and egg yolk, then gradually mix in the flour.

Step 2 of 5

Divide the dough in half. Knead cocoa powder into one portion. Wrap both portions and chill for 40 minutes.

Step 3 of 5

Roll each portion into 18cm squares. Slice into 2cm wide strips. Layer white and cocoa strips, brush with egg wash, and press together. Repeat for three layers. Chill for 15 minutes.

Step 4 of 5

Preheat oven to 180°C. Slice the chilled dough into 1cm thick pieces, place on a lined tray, and bake for 15-20 minutes.

Step 5 of 5

Allow cooling for 2 minutes before serving.