S'mores are traditionally cooked over a campfire, although they can also be made at home over the flame of a wood-burning fireplace, in an oven, over a stove's flame, in a microwave or with a s'mores-making kit. A marshmallow, usually held by a metal or wooden skewer, is heated over the fire until it is golden brown. Traditionally, the marshmallow is gooey but not burnt, but, depending on individual preference and cooking time, marshmallows can range from barely warm to charred. The roasted marshmallow is then sandwiched between two halves of a graham cracker and a piece of chocolate (or with chocolate on both top and bottom), between the graham crackers.[8] An additional step may follow, wherein the entire sandwich is wrapped in foil and heated so that the chocolate partially melts.

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Various confections containing graham cracker, chocolate, and marshmallow are often sold as some derivative of a s'more, but they are not necessarily heated or served in the same shape as the traditional s'mores. The Hershey's S'mores bar is one example. Kellogg's Pop-Tarts also feature a s'mores variety.