Pipe guests' initials onto the tops of these cupcakes, or create a message that is spelled out when the cupcakes are lined up.
Place chocolate, cream, and butter in the top of a double boiler or a heat-proof bowl over a pan of gently simmering water. Stir occasionally until melted. Remove from heat; let cool slightly. Transfer to a bowl; dip each cupcake into glaze, letting excess drip off. Chill until just set, about 10 minutes.
In the bowl of an electric mixer fitted with the paddle attachment, combine egg whites and sugar on low until spreadable. Add food coloring, if using. Transfer to a pastry bag fitted with desired tip, and pipe immediately (or store in an airtight container 1 to 2 days; beat with a rubber spatula before using).
Raw eggs should not be used in food prepared for pregnant women, babies, young children, the elderly, or anyone whose health is compromised.