The room isn't especially appetizing: glossy white walls lit by fluorescent lights, shelves and revolving displays crammed full of cookie cutters, hard-candy molds, plastic bride and groom figurines, and tooth-cracking ornaments. The surroundings may not be so tasty, but the cake decoration classes run by Lynette Clarke in the back of Prospect Heights' Cake Works certainly are. The classes, which cost around $10 per hour, run from frosting basics to the pinnacle of dessert adornment: gum-paste flowers, edible cake tops, bas-relief appliqué, bridge and extension work. On a recent afternoon, behind a table littered with plastic molds and Argo cornstarch, Clarke, a 25-year resident of Brooklyn, presided over a class on fondant icing falls and frills, while her school-age son tidied supplies. Clarke was strict but friendly as she trimmed lace-like strips of icing with a pastry knife or urged her students to lean into their pastry rollers. As one of the mothers at the table pulled an embellished strip of fondant free of its mold, she couldn't help happily exclaiming, "Oh! Oh! My, my, my!"