For the vanilla cookie dough, cream the butter with the sugar (sachet 1) for 1 minute until pale and creamy, then mix in the egg yolk until well combined. Add the cookie mix (sachet 2) and stir to form a smooth dough – you may need to use your hands to bring the dough together towards the end. Set aside

Prepare the chocolate cookie dough in a separate bowl following the same method above.

Lay a piece of cling film on your counter top. Working with only half of each dough, break off pieces of dough and press together to create a marbled pattern. Shape the marbled dough into a log about 4-5 cm in diameter and wrap tightly in the cling film.

Repeat with the remaining halves of dough to form two cookie logs. Place the logs in the freezer for 30 min – 1 hour until firm.

Preheat your oven to 160°C (fan-assisted convection) and line two oven trays with baking paper.

Unwrap a cookie log and use a thin sharp knife to cut it into 5mm-thick slices – you can bake both logs now or keep the second log, unsliced, in the freezer for future use. Space the cookies on the prepared baking trays.

Bake for 10-12 minutes or until the cookies are crisp and lightly golden. Allow to cool on the trays for 5 minutes before transferring to a wire rack to cool completely.

Tip: Each log makes 20-25 marbled cookies. If your cookie log breaks apart when you’re slicing it, set it aside at room temperature for a few minutes to warm up before trying again.