Six kids get a lesson on decorating cookies and cakes from sugar artist Margaret Braun.

When Margaret Braun, the goddess of sugar artistry, agreed to host a cookie- and cake-decorating class for kids, I was ecstatic. She's incredibly talented—and patient. The author of Cakewalk, she's made cakes for architect Maya Lin and artist Louise Bourgeois, and has recently been collaborating with superstar party planner Colin Cowie on weddings. She might drive to Vermont from New York City, where she lives, with 150 mini cakes in her van—or fly to L.A. with one big cake on her lap. Her creations will make their movie debut in The Great New Wonderful, due out next year, in which Maggie Gyllenhaal plays a cake designer. (The director actually hired Margaret as a consultant.)

Even though she's an Artist with a capital A, Margaret knew instinctively how to work with kids—and the importance of planning ahead. The night before the class, she baked a chocolate layer cake and gingerbread girls. She rolled out white fondant (sugar paste) to blanket the cake and covered the girls in white dresses made of royal icing. She mixed a batch of pastillage (a sugar paste that turns as hard as porcelain), rolled it out and cut it into ornament shapes. Finally, she had three kinds of blank surfaces ready to decorate—"like pages in a coloring book," she explains.

The day of the party, Margaret dusted a worktable with cornstarch, then set out tools and decorations: cookie cutters, dragées (balls of sugar coated in shiny silver), colored fondant ("like Play-Doh," Margaret says), pastry bags and tips, food coloring and royal icing. "It's chaos at first, then the kids focus right in," she said when the children arrived. Five nine- and 10-year-olds—and one precocious four-year-old—listened earnestly to Margaret's instructions, then got to work pushing cookie cutters into colored fondant and squeezing royal icing out of pastry bags. The results were unusual and lovely: a pastillage snowflake swirling with silver dragées; a gingerbread girl with blue Christmas trees on her skirt.

"I wish I could work like a child," Margaret says. "I'm obsessed with symmetry. But kids make a mess and end up with beautiful, abstract things. You might not know what they're thinking, but they know exactly what they're doing."