Melt the chocolate in the microwave in 30 second bursts until just melted.
Once set, remove the slice from the baking tray and set on a large chopping board. Lay the rest of the biscuits over the top, side by side leaving the edges exposed. Trim away the edges, then cut the slice into even pieces using the biscuits as your guide.
Melt the chocolate in the microwave in 30 second blasts. Crush 1-2 biscuits into crumbs.
Dip one end of each piece of slice into the chocolate, then sprinkle the top with biscuit crumbs. Sit on a wire rack for 5-10 minutes until the chocolate is just starting to set, then transfer to a sheet of baking paper on a plate in the fridge to set, then serve.