Dissolve sugar and water over low heat. When sugar has dissolved, bring to a boil. Allow to boil without stirring for 2-3 minutes. Continue to boil until syrup is a deep amber caramel color, gently swirling or scraping the bottom of the pan. Reduce heat and add butter, stirring until melted. Remove from heat and add cream (mixture will suddenly froth). Stir in vanilla and pour caramel in a jar, it will thicken more as it cools.
Preheat oven to 350 and grease an 8 or 9″ springform pan. Melt chocolate and butter in a saucepan or double boiler and stir til smooth. Set aside and cool. Beat eggs and sugar on medium speed til thick and pale, around 4 minutes. Fold in chocolate and vanilla. Pour and bake 45 minutes. Cake will sink after removing from oven. Do not remove from pan.
Slice 2 bananas into the well in the cake. Pour the caramel sauce over bananas (warm slightly in microwave if caramel has been chilled). You should have a fairly smooth surface. Allow to chill several hours or overnight.
On the stove, heat cream just to boiling. Pour over chocolate and let sit 10 minutes. Stir til smooth. Cool, stirring occasionally, to achieve a thick but pourable consistency.
With cake still in pan, pour ganache over caramel. Start in the center and work your way outward in a spiral. Chill until set. Before serving, run a knife around the inside of the pan and remove the sides of the pan.