In the U.S. we seem to wear cinnamon blinders. Most of what we enjoy and call cinnamon in this country is Cinnamomum aromaticum or C. loureiroi, also known as cassia. It's the brash, bold, sweet-and-spicy stuff we love in our cinnamon buns and gingerbread. It's pretty awesome.
But it's not the only cinnamon out there. In the past, when people talked about cinnamon, they were talking about C. verum (née C. zeylanicum when Sri Lanka was called Ceylon). It's not the cinnamon Americans are used to—it's much more mellow and subtle—but it's worth expanding our horizons for.
Known as canela in Mexico, Ceylon cinnamon, or "real" cinnamon, C. verum is milder than its brash counterpart cassia. It's far less spicy, and if sampled with expectations of cassia it may disappoint. Its flavor tends toward vanilla: a warm floral note with hints of heat and honeyed fruit. Though it's milder, "true" cinnamon possesses a deeper cinnamon flavor that plays well in the background of dishes, especially savory ones.
Ceylon cinnamon can be identified by the shape of its stick (called a quill). Cassia sticks are what we stir into our hot cider: the quills are short and the bark is firm and thick. Ceylon quills, on the other hand, are long and curl around themselves like a scroll. Their bark is thin, delicate, and flakes easily.
Ceylon Cinnamon versus Cassia
Frankly, if I could only have one, I'd keep around cassia—specifically C. loureiroi, commonly called Saigon cinnamon. It has the richest, spiciest flavor thanks to its exceptionally high oil content. Fortunately I don't have to choose, so I keep both Ceylon and Saigon cinnamon around.
Saigon cinnamon plays best in most traditional Western applications: cookies, pies, cakes, ice creams, sweet breads, and garnishes for hot drinks. Its bold flavor stands out well against all that fat and flour, and its spicy tinge gives satisfying dimension to sweets. Recipes that call for cinnamon in addition to clove, nutmeg, or allspice take well to Saigon cinnamon; its spice plays well against their sweetness. It's also a great pairing for chiles.
I find Ceylon cinnamon works better with fewer competing flavors. Its subtle taste and aroma take especially well to chocolate, vanilla, dark liquors, and citrus. While Saigon's spice plays best against crisp apples, Ceylon's warm coziness is the perfect match for oranges. Ceylon cinnamon also plays well in savory applications; its demure character sinks to the background of rich sauces well, such moles or bean broths (especially with some orange juice and peel thrown in).
Chinese recipes calling for cinnamon usually refer to cassia (it's one of the ingredients in five spice powder), as that's where most cassia originated. Southeast Asian and Mexican cuisines are much more fond of Ceylon cinnamon. It's the key ingredient in Mexican hot chocolate, with its telltale smooth flavor and rich aroma.
Where to Find Cinnamon
Cinnamon is one of the few spices I prefer to purchase pre-ground. It's difficult to get a fine powder with an electric grinder, and even small chunks feel unpleasantly gritty. So I make sure to use it quickly (within 6 to 8 months) and source it well. Mexican markets carry reliably good Ceylon cinnamon (look for it as canela). Otherwise I head to a reputable spice merchant. The Spice House carries superb Ceylon ($8 for 4 ounces) and Saigon cinnamon ($5.29 for 4 ounces), both of which I like to keep on hand.