Line a square 25 cm/10 inch shallow baking tin with cling film (plastic wrap).
First make the base. Put the nuts in a food processor and pulse until finely chopped. Add the coconut oil and cocoa powder and process again to combine. Finally, add the dates and process until smooth. I like it with a few chunky pieces of nuts through it.
Tip the mixture into the baking tin and pack it down evenly. Transfer to the fridge for 2 hours.
When the base is ready, make the topping. Mix all the ingredients together in a bowl and stir until combined. Pour the mixture over the base and use a spatula to spread it out evenly. Return the bars to the fridge for another hour until the chocolate topping has set.
Slice into 15 pieces and serve. These bars melt quickly, so are best stored in the fridge until you are ready to eat.