In a mixer, cream the butter and sugar together for 2-3 minutes
Add the egg and sugar and continue mixing
Melt the chocolate and add in the mix
Line a cereal bowl with plastic wrapping paper. Add some chocolate buttercream on the bottom and on the sides
Sprinkle in the cereal. Cover with buttercream. Add another layer of cereal and top off with remaining buttercream. Close it off with the plastic wrapping paper and place in the fridge for a minimum of 4 hours
When the chocolate sets ups, sprinkle with crushed cereal and shaved chocolate