Butter an 9-inch round cake pan (about 2 inches deep) and line bottom with a round of parchment paper or foil.
In a small bowl whisk together cocoa powder, flour, cornstarch, and baking soda.
In a metal bowl whisk together whole eggs, yolk, sugar, and salt until combined. Set mixture over a saucepan of simmering water and continue to whisk until lukewarm. Remove bowl from heat and with an electric mixer beat mixture at high speed until it has cooled and doubled in volume.
Sift one third cocoa mixture over egg mixture and fold together. Sift and fold in remaining cocoa mixture, half at a time, in same manner. Pour batter into pan and smooth top. Bake génoise in middle of oven for 30 minutes, or until it is firm to the touch and pulls away slightly from side of pan. Invert génoise onto a rack and immediately invert onto another rack to cool right side up. Génoise may be wrapped in plastic wrap and chilled 1 week or frozen 1 month. Thaw génoise before assembling cake.
In a saucepan bring cream, butter, and corn syrup to a boil over moderate heat and remove pan from heat. Add chocolate, swirling pan to submerge chocolate in hot mixture, and let stand 3 minutes. Whisk ganache until smooth and transfer to a bowl. Chill ganache, covered, at least 2 hours and up to 3 days.
Let ganache stand at room temperature until slightly softened and pliable but still cool. With a whisk or electric mixer beat ganache just until light and fluffy.
Remove parchment paper from génoise and with a long serrated knife cut cake horizontally into 3 rounds.
Invert top layer of génoise onto a springform pan base or a 9-inch cardboard round and brush with one third syrup. Spread layer with half of jam and spread one third ganache over jam. Top ganache with middle layer of génoise and repeat layering of, jam, and ganache. Top with third layer of génoise. Spread top and side of cake with remaining ganache. Chill cake until ganache is set, about 30 minutes. Cake may be assembled ahead, wrapped in plastic wrap, and chilled 5 days or frozen 1 month. Thaw cake before proceeding.
In a saucepan bring cream to a boil and remove pan from heat. Add chocolate, swirling pan to submerge chocolate in hot cream, and let stand 2 minutes. Whisk glaze until smooth and pour through a sieve set over a bowl. Cool glaze to room temperature.
With cake on a rack set over a pan (to catch drips) pour glaze through sieve onto center of cake. Quickly spread glaze evenly over top and sides of cake with a long, narrow, metal spatula. Let cake stand until glaze is set, about 5 minutes.
Garnish cake with raspberries and keep at cool room temperature until ready to serve.