While cookies made from almond flour and egg whites have been around since at least the 16th century, the concept of filling them and sandwiching them together to create what we know as a macaron is a 20th century invention, popularized by the Parisian pastry shop Ladurée . Typically the shells are colored to reflect the flavor of the filling, which can be anything from buttercream to ganache to jam. You can eat the filled cookies right away, but they're best after a day or two, as the shells will soften slightly and absorb the flavor of the filling, yielding a tender, pillowy cookie. Get the recipe for Macarons »