Preheat overn to 350?

Cake:

In bowl, cream butter with sugar until fluffy. Beat in eggs, one at a time, then vanilla. Beat in sour cream. Combine flour, baking soda and chocolate; add in 3 additions to creamed mixture alternately with 2 additions of bananas, mixing just until flour is incorporated. Spoon into 2 greased 8 1/2 in springform pan, smooth tops. Bake in oven for 35-40 miuntes or until tops spring back when touched. Let cool on rack for 20 minutes. Remove sides of pans; let cool completely.

White Chocolate Frosting:

In a saucepan, briong 1 1/2 cups cream to boil; pour over white chcolate in bowl, whisking until melted. Add vanilla. Refrigerate until chilled, 1 hour, whisking often. On medium speed, beat chocolate mixture just unil ridges hold shape. Beat remaining 1 1/2 cup cream until soft peaks form; gently fold into chocolate mixture.

Assembly:

With a serated knife, slice cakes in half horizontally. Place a top layer, cut side up, on a plate. Spread top with 3/4 cup icing, cover with a single layer of bananas, leaving 1/2 in border. Cover with 1 bottom layer, cut side down; reapeat with icing and bananas. Repeat with remaining top layer, cut side up, and some of the icing and bananas. Top with remaining cake layer, cut side down. Using palette knife, cover cake smoothly with remaining icing. Refrigerate until firm about 1 1/2 hours.

Ganache:

Meanwhile, bring cream to boil, pour over chocolate in small bowl, whisking until melted. Let cool for 20 minutes or until room temp and still pourable. Pour over the center of the cake, spreading to edge with clean palette knife, if necessary, and letting some flow down sides. Refigerate until firm about 40 minutes or up to 1 day. To serve, drizzle melted chocolate with fork over remaining bananas; let sit. Arrange on top of cake.