300gm butter,at room temperature
1/2 tsp vanilla essence
120gm icing sugar,sifted
400gm plain flour,sifted
30gm cocoa powder,sifted
1 egg white,beaten
1. Mix butter,vanilla,sugar and flour with electric beater or dough hook on low to medium speed until mixture forms a smooth dough. Divide dough into two portions. Mix cocoa powder into one haft. Chill dough until it firm enough to work with. Roll out plain and chocolate dough into squares of equal size,to 1cm thickness. Cut each sheet into 4cm-wide strips.
2. Brush 2 chocolate strips with egg wash and place 2 plain dough strips on the top. Brush the top of 1 strip with egg wash and stack the other strip on top s that you get a block of alternating coloured layers. Brush 2 plain dough strips with eggwash and place 2 chocolate dough strips on top. Brush the top of 1 strip with egg wash and stack the other strip on top so that you get a block of alternating coloured layers.
3. Cut each block lengthwise into strips of 1cm thickness,If dough is too soft,chill before working. Stack the strips to form a 4x4 checkerboard pattern,brushing with egg wash to bind between layers. Cut crosswise into 6mm-thick pieces and place on sheet pans lined with baking paper. Bake at 180c until gloden brown for 15 mints or at 160c for 20 mints.