Melt the Mars bars and butter together in a pot, then mix the Rice Krispies in with them, coating the cereal completely.
Transfer to a well greased 9×9 or 8x8 pan.
Melt the chocolate and butter for the topping, stirring until smooth, then pour it on top.
Cool in the fridge then cut into pieces and serve.
If you don't have Mars Bars, you can use Three Musketeers bars in the US!ACTUAL calories and nutritional information is going to depend on what chocolate bar you use! These values are just approximate!