The chef of the Trellis Restaurant in Williamsburg, Va., Desaulniers (Death by Chocolate) offers 50 extravagant, elaborate, indulgent chocolate cakes. These are not treats for the kitchen shy, requiring as they do many phases and, within each phase, many steps. But the outcome is so luscious and Desaulniers is so charming and persuasive, it's hard to believe it's not time well invested. Sprinkled liberally throughout are anecdotes about the author's mother, his childhood and various recipe contributors, who include friends and family members, fellow pastry chefs and their relations. There are cakes served at the Trellis as well as recipes handed down from generation to generation and those discovered "on the road." Recipes for adorable baby cakes, whose size belie the intensity of their flavor, include Heart of Darkness Cakes, in which bakers are instructed to "remove the muffin tin from the oven and, moving quickly, place a single frozen truffle in the center of each portion of cake batter." Chocolate Chunk Cookie Cakes meet the demand for a tasty confection that can withstand the indignity of being plopped in a lunch box. There are also big event cakesAamong them, Julia's [Child] Eighty-fifth Birthday CakeAas well as cakes from out of town, such as The King's Chocolate Peanut Butter Banana Bourbon Cake, based on Elvis's favorite sandwich. The book concludes with an assortment of accompaniments, such as instructions for chocolate honey and a recipe for a wicked cocktail called Chocolate Temptress (think vodka and Frangelico). Many of these confections go over the top, but chocoholics will eagerly follow Desaulniers wherever he leads. (Sept.)