favourite patisseries - Northern France

I can't believe I'm responding to this, because I never encountered a bad French patisserie, and I didn't usually pay attention to where I was buying things. However, in Reims, I actually did notice where I was: near the market at Maison Caffet. I went there twice, it was so yummy.

In Rouen: Ma Boulangerie in Rue Armand Carrel (ten minutes walking east of the cathedral) is a Meilleur Ouvrier de France, a prestigious award of a craftsmen competition in France, held every four years.

Thank you for both suggestions. I have to agree that I have never had a "bad" experience but all you fellow travelers usually can identify the amazing ones.