Cake:

1. Preheat oven to 350 F F. Grease two 9" x 1 1/2" round cake pans. Line the bottoms with parchment or wax paper. Grease again and flour.

2. In a food processor puree the bananas. Blend in the yogurt. Add the eggs and vanilla and pulse a few seconds to combine. Set aside. Whisk flour, sugar, baking powder, baking soda, and salt in medium mixing bowl. 3. In a large mixing bowl cream the butter with an electric mixer until smooth and light. Add 1/2 the banana mixture and all the dry ingredients. Mix on medium speed two minutes until light and fluffy. Add the rest of the wet mixture and beat on high speed for one minute. Fold in grated chocolate.

4. Divide the batter evenly between the prepared pans, which should be half full. Bake for 30-32 minutes or just until a toothpick inserted in the center comes out clean. Cool on a rack for 5 minutes. Run a small, metal spatula around the sides, then unmold and peel off the paper lining. Cool the cake to room temperature before assembling.

Frosting:

1. Heat cream and chocolate in a heave saucepan over low heat, stirring occasionally to melt and blend the chocolate. Remove from the heat, stir in the powdered espresso, then pour into a clean dry container. Once the cream reaches room temperture, cover directly with plastic wrap to prevent a skin from forming. Chill in the freezer until very cold, about 1 hour, or refrigerate for up to 3 days.

2. Once the cake has cooled to room temperature, beat the ganache (do not use a whisk beater) on medium-low speed to soft peaks. Increase to high speed and continue beating until the frosting reaches a thick spreading consistency. Spread the frosting immediately, while it is smooth.

3. Frost as desired for a festive look: spread 3/4 cup of frosting between the layers and another 3/4 cup on top. Mask the sides with a very thin layer. With a pastry bag fitted with a large open star tip pipe a continuous vertical pattern all around the sides. Pipe stars around the top of the cake. Finished, the cake keeps refrigerated up to 3 days. For best results slice the cake chilled, but let sit 1/2 hour at room temperature before serving.