This is a recipe 1 of my SIL's shared with me.

Mars Bar Slice

Ingredients
1x 12 pk of mars bars
3 tbsp margarine/butter (whatever you have)
3 cups rice bubbles

Method
1.chop mars bars into small pieces, place in saucepan & melt over low heat. Add margarine/butter & melt. When this has melted, add rice bubbles & mix well.
2. pour mixture into a lined tray & place into the fridge.
3. when cool, cut into bite size squares.

I've made this many times, sometimes i even double the recipe so its a little higher/thicker.