Culinary Notes
The Clarity Rule: Use sticks when you want the liquid to remain transparent or light. If you are poaching pears in white wine or making a Vietnamese Pho, a stick provides a clean, elegant infusion. Powder would turn the liquid cloudy and brown.
Cassia vs. Ceylon (Visual): You can tell the variety instantly by looking at the stick. Cassia (common) is a single, thick, hard piece of bark curled inward. Ceylon (true cinnamon) looks like a tight cigar, made of many thin, flaky layers rolled together. Ceylon is much easier to grind yourself; Cassia is tough enough to break a coffee grinder.
Reusability: Unlike most spices, a whole cinnamon stick is robust. If you have only steeped it in a light syrup or rice for a short time, you can rinse it, dry it, and use it again. The flavour will be subtler, but still present.
Toasting: To wake up the oils, toast the stick in a dry pan for 60 seconds before throwing it into your liquid. You will smell the difference immediately.