Les Co'Pains D'abord is, imho, the home of the very best tasting and most beautiful full-butter croissant in Montreal. One is not sure whether to just stare at it, take a picture or show it off it's so pretty. The indecision completely vanishes once you have a bite of this buttery piece of heaven. The problem then becomes stopping yourself before your liver decides to vacate your body.
All the pastries I have tried there over the years were all delicious. I am partial to the raspberry clafoutis that has a rich and creamy filling in a buttery cookie crust.
The bakery on Mont-Royal (there are 2 other locations on Masson close to 4th Ave. and Rachel close to St-Denis that I never visited) has a small area to order and offers only 6 or 7 tables to sit at. I usually go there on weekend mornings when it's bursting at the seams with customers. Even then, there are so many clerks behind the counter that the wait is never more than 5 min. to be served.
They also have very good coffee and hot chocolate.