For this confection, Brenda and Mary Maher of Cakegirls created a baroque arrangement of shells on a simple monochromatic cake iced with fondant, since its thick consistency stands up better than buttercream to warm weather. The Mahers made these intricate treasures by pressing fondant into molds of actual scallop, clam and snail shells; faint lines of peach-colored iridescent powder add detail to each mollusk.