Here are blogs that shows how to make this type of apron:
Matrilda la Zouche´s Wardrobe - this one is really great and was the one that I got a lot of "how-to-do" information out off.
This is the end product - Louise (yes she has the same name as me :0)) is very happy with it and have worn it to two markets during the summer. She gets a lot of questions and "oh that is really nice" so that makes me want to make one during winter for myself. I think I might make the combes a bit smaller so that they don´t open quite as much.
Here are some pictures that show how I made the smock/pleat effect:
This picture shows how I made marks on the fabric (the blue dots) and have sewn it with a bight colour thread so that I can see it when I have sewn the combs together (the the next pictures)