Usually, cookie bars are around 2cm - 2.5cm (or 1 inch) thick. You can make them thinner if you prefer. Just remember that thinner bars will bake quicker so you’ll need to knock a few minutes off the recommended cooking time. You might also want to break up the Mini Eggs if you are making thinner bars. The best way to do this is to put them into a sealed food bag and bash them with a rolling pin.