Like I mentioned above, cutting Cadbury creme eggs in half can be hard because the inside is creamy goodness that will just run all over the place. I stick my creme eggs in the fridge or freezer for 30 minutes- 1 hour before cutting them. Make sure to peel the foil wrapping off BEFORE you get them cold. Trust me, I learned the hard way that the foil is much harder to get off when they are frozen  Once they are chilled and ready to be put on the brownie batter, I carefully cut along the side where the chocolate shell meets and you see a line (be careful). It should cut fairly easily that way! Don't worry if they break, they will still taste great on your brownies!