For the syrup, combine the sugar and water, bring to a boil and cool. Stir in the liqueur.
For the chocolate filling, bring the cream to a boil. Remove from heat, add the chocolate, and allow to stand 2 minutes. Whisk in the butter until smooth and cool.
To make the Bavarian, combine the raspberries and sugar in a saucepan. Bring to a boil and simmer 10 minutes. Use a food mill or a fine sieve to puree and strain away seeds. Cool. Combine the liqueur and gelatin in a small, heatproof bowl and soak 5 minutes. Place the bowl over simmering water to make liquid again, then whisk into cool puree. Whip cream and fold it in.
Slice the genoise into two layers and place one in the bottom of a 10-inch springform pan. Moisten with half the syrup. Whip the cooled chocolate filling to lighten and spread half over cake layer; pour on half the Bavarian. Repeat with remaining cake layer, syrup, chocolate filling, and Bavarian. Chill to set.
To unmold, run a small knife between dessert and mold and lift off side of pan. Whip the cream and spread over sides of dessert. Press some of the chocolate shavings into cream. Arrange raspberries on top in two concentric circles around the top rim, then sprinkle center with shavings and confectioners' sugar.
One 9 by 2-inch round layer pan, or a 9-inch springform pan, buttered and the bottom lined with a disk of parchment or wax paper Set a rack at the middle level of the oven and preheat to 350 degrees. Sift together the cake flour, cornstarch, and cocoa through a fine-meshed strainer over a piece of waxed paper to break up any lumps in the cocoa. Set sifted ingredients aside with the strainer. Whisk together the eggs yolks, sugar, and salt in the bowl of an electric mixer. Place the bowl over a pan of simmering water and continue whisking gently until the mixture is lukewarm, about 100 degrees. This should take only a minute or two. Whip with the electric mixer on high speed until the mixture is cooled and increased in volume, about 3 to 4 minutes. Remove bowl from mixer and sift in dry ingredients, in three additions gently folding each third in with a rubber spatula. Pour the batter into the prepared pan and spread the top even with a spatula. Bake the layer about 30 minutes until it is well risen and the center is firm to the touch. If necessary, loosen the layer from the side of the pan with a small knife or spatula and invert the cake onto a rack. Place another rack on the cake and invert again. Remove the top rack, so that the layer cools right side up, still on the paper. Yield: 1 round layer, 9 inches in diameter by 2 inches deep