In recent years, many people have argued that French macarons are displacing cupcakes as the trendy sweet treat. And why not? These diminutive treats are smaller, gluten-free, and come in a wide variety of flavors. They're also becoming easier to find, with many bakeries doing a brisk business selling them alongside other pastries.

In theory, these sandwich cookies are stunningly simple to make: they are just egg whites beaten with sugar—meringue—with ground almonds folded in. But they are surprisingly tricky to make well, to which many troubleshooting guides on the internet can attest. A poorly-mixed meringue can leave air pockets that yield hollow cookies. The wrong temperature can make cracked tops. The list of possible problems can go on and on.

So what makes a "perfect" macaron? The glossy shell on the outside should be smooth with a light sheen, providing the thinnest veneer for soft chewy interior. Each cookie should have a "foot"—that thin little ruffle going around the bottom. The ratio of cookie-to-filling should be between 1:1 and 2:1. And the filling itself? Ganache fillings should be smooth and jams shouldn't be cloyingly sweet; the goal is to not overwhelm the flavor of the cookie.

While macarons can now be found in places like Starbucks or the frozen foods aisle of Trader Joe's, finding a good one can be a challenge. Here are the places to look for D.C.'s best examples. And soon, get ready for French macaron experts Laduree to open in Georgetown, though they haven't given an estimate for the timing of their arrival.