If you're not willing to sit down for a full-blown experience, but still need a mid-day pick-me-up:
Go to the side counter ("Chocolate Bar") and order a Grandma-style hot chocolate to take out. Hedging our bets, we ordered a Dark Semi-Sweet (how can you lose?), with the addition of a little extra milk. Intense, thick, smooth, and not overly sweet, this is just about the perfect cold-weather beverage.
For tourists, an absolute necessity. You'll need the extra calories to power up and down the Boulevard St Laurent. (Plus, the cute items in the display case up front will make good gifts for the folks back home.)