Important sewing advice: Don't eat and sew!
Materials: 1 bar of chocolate, 2 colors of pearl cotton and a needle
Make the holes before stitching. Use a needle held in the flame of a candle shortly. The holes will get larger than the needle, so use a normal size needle - not an oversized one. Keep the bar in the fridge for some time before starting to stitch.
The thread will smudge with chocolate so you probably have to change it frequently.