Line the base and sides of a 20cm square cake tin with baking paper - making sure you leave paper hanging up the sides of the tin to help you remove the slice once it has set.
Crush the biscuits until they form small pieces and place in a large bowl.
Add the melted butter, cherries, coconut and pink colouring and mix until well combined.
Transfer to your prepared tin and use the back of a spoon to flatten the top of the mixture - don't worry, it will be sticky!
Place the dark chocolate and coconut oil (if using) into a microwave safe bowl and cook on 30 second spurts until it's just melted.
Pour the melted chocolate over the top of the slice and place into the fridge for 3 hours or until set. Once set, cut into pieces and store in an airtight container in the fridge for up to 7 days.