Grease and line a 22 X 28cm rectangular slice tin with baking paper and set aside.
Crush the chocolate biscuits and Oreos until they resemble fine crumbs.
Add the condensed milk and melted butter to the crushed biscuits and mix well to combine. If your mixture is too crumbly, add a little more condensed milk.
Press the mixture firmly into the prepared tin and place into the fridge.
Break the Cookies & Cream chocolate into pieces and place into a microwave-safe bowl. Add the coconut oil and melt in the microwave on 50% power for 3-4 minutes (stirring every 30 seconds), until just melted.
Pour the melted chocolate over the chocolate base and place back into the fridge for 3-4 hours to set.
Cut into slices using a hot knife and store for up to 1 week in an airtight container in the fridge.