Melt 250g of butter and a 200g bar of dark chocolate. Whilst this is melting, break up a 400g packet of digestive biscuits until you have a mixture of fine crumbs and some larger chunks (I usually put them in a plastic bag and beat them with a rolling pin).
Once the chocolate mixture is melted, mix the two together and then press the mixture into a baking tray. Leave in the fridge overnight, and then it’s ready to cut up and eat.
Serving suggestion: it’s lethal with whipped cream.
Possible variations: I quite fancy trying it with a bit of mint flavour.
Healthier version: may be some of the butter could be substituted with milk?
Note that the ingredient proportions are pretty approximate as I tend to just go by packet size, which differs between England and Holland… I have seen various different recipes, some of which require you to add brown sugar or syrup. So if you don’t like this variant, experiment!