Pain au chocolat

In France, we had convenient log bars of chocolate to use when making pain au chocolat. The first time I made them here, I used a well known brand of cooking chocolate (supposedly high quality), that starting melting when the pastries were proving. This time I used some different chocolate and also some "buttons" which were much more successful.

I can't fail to hear my tutor's voice in the background "All the pain au chocolat should be consistent in size" Oh dear!