Some plain croissants are straight, and some are joined together at the ends in a sort of crescent moon shape. I never knew that this actually meant something. I thought the shape of the croissant was simply the preference of the person who had shaped them.What I learned recently is that the shape of the croissant - straight across or crescent moon, reflects the ingredients inside... in France at least. In France, it is the law, that only a croissant made with pure butter can be straight. If a croissant is made with any other sort of fat, for example, margarine, it must be joined at the ends to form a crescent moon shape.The next time you buy a croissant, you might be a little more inquisitive about what it's made of...