Use a food processor to chop the biscuits into textured crumbs. If you like your slice a little chunkier then you can also smash up the biscuits in a plastic bag, using a rolling pin. I put mine in the Thermomix and pulse for about 4 seconds.
Pour the biscuit crumbs into a bowl and add the coconut. Melt the butter and then pour it into the biscuit mixture and combine.
Press the mixture into a lined slice tin (20×20 cm or 15×30 cm)
Melt the chocolate and the coconut oil together. If you prefer a hard chocolate top, leave out the coconut.
Refrigerate until the top is set and slice into 24 pieces.