Ingredients

• 250g butter, softened
• 1 cup caster sugar
• 2 teaspoons vanilla bean paste
• 1 egg
• 2 1/2 cups plain flour
• 2 tablespoons Dutch-processed cocoa
• 1 tablespoon milk

Method

• Step 1 Using an electric mixer, beat butter, sugar and vanilla for 5 minutes or until light and fluffy. Add egg. Beat until just combined. Stir in flour until just combined. Transfer 2/3 of the dough to another bowl. Add cocoa and milk to remaining dough. Mix well.
• Step 2 Knead 1/2 of the remaining plain dough into a ball. Roll and shape dough into a 30cm long log. Wrap in baking paper and freeze for 20 minutes or until just firm. Knead chocolate dough into a ball and wrap in plastic. Repeat with remaining plain dough. Refrigerate until required.
• Step 3 Roll chocolate dough between 2 sheets of baking paper until 3mm thick. Cut into a 20cm x 30cm rectangle. Unwrap cookie log and place along 1 long side of chocolate dough. Roll up dough to enclose log. Wrap in baking paper. Freeze for 15 minutes.
• Step 4 Roll out remaining dough between 2 sheets of baking paper until 3mm thick. Cut dough into a 25cm x 30cm rectangle. Unwrap cookie log and place along 1 long side of dough. Roll up dough to enclose log. Wrap in baking paper and freeze for 30 minutes or until firm (see note).
• Step 5 Preheat oven to 180°C/160°C fan-forced. Line 3 large baking trays with baking paper.
• Step 6 Unwrap cookie log. Using a flat-bladed knife, cut log into 1cm-thick slices. Place, 3cm apart, on prepared trays. Bake, 1 tray at a time, for 10 to 12 minutes or until edges are just starting to turn light golden. Stand on trays for 5 minutes. Transfer cookies to a baking paper-lined wire rack to cool completely. Serve.