I figured this out back in my waitressing days and we had leftover carrot cake. I LOVED the carrot cake but by the time it made it home, I had lost half the frosting which I thought was the best part. I started cutting the cake through the middle and flipping the top to the middle so I didn't lose one little bit of frosting. Worked like a charm.
Now I use this trick for my kids lunch boxes when we have left over cake or bars.
Here's your bar