• Spray a 20cm square cake tin with cooking spray, then line with baking paper and set aside.
• Place biscuits onto a sheet of baking paper or a silicone mat and crush them with a rolling pin, keeping some small chunks amongst the crumbs.  Set aside.
• In a large saucepan, melt the butter and caster sugar, mixing until sugar has melted and beginning to bubble.
• Add cocoa and mix well, then remove from the heat to cool slightly for a 2 minutes.
• Stir in the beaten egg, coconut, crushed biscuits and walnuts.
• Press mixture firmly into your prepared tin.  Placing a sheet of baking paper over the hedgehog mixture and running the back of a spoon firmly along the surface will smooth out the mixture and prevent your spoon from sticking.  Pop the slice into the fridge while you make the frosting.

Chocolate Frosting

• In a medium bowl, cream the butter and icing sugar.  This can be done with either a rotary whisk or a handheld electric mixer.  It will remain crumbly.
• Add boiling water to the cocoa and mix into a paste.  Add the cocoa mixture to the butter and icing sugar, them mix again.  The frosting will come together into a smooth, stiff mixture -feel free to add a tiny bit more boiling water if you need to.
• Spread the frosting over the hedgehog slice and make little swirly patterns.  Pop in the fridge for the frosting to firm up a little, then slice into squares.