Chocolate Banana Cream Cake

Steps

1. For cake, preheat oven to 350°F. Spray two 9" layer-cake pans with vegetable cooking spray. Line bottoms with wax or parchment paper; spray paper. Dust pans with flour; tap out excess. In a small bowl, using a fork, mash 2 bananas.
2. In a medium bowl, stir cake flour, cocoa, baking powder, baking soda and salt; set aside. In a large bowl, with electric mixer set at medium-low speed, cream margarine and sugar until light and fluffy, about 5 minutes.
3. Beat in eggs, one at a time, beating well after each addition. Beat in mashed bananas and vanilla extract. Reduce speed to low; beat in the flour mixture in thirds, alternately with the buttermilk, until just mixed.
4. Pour into prepared pans. Bake 30-35 minutes until a pick inserted into the center comes out clean; cool in pans on racks 10 minutes, then invert pans onto racks to cool completely. At this point, if desired, layers can be wrapped in foil and stored in the refrigerator for 1-3 days. Unwrap and bring to room temperature before continuing.
5. For the filling, in a small saucepan, combine the flour, sugar and a pinch of salt. In a small bowl, beat 1 1/2 cups milk and egg yolks; stir into flour mixture until smooth. Cook over medium-low heat, stirring constantly, until the mixture thickens and comes to a boil; continue boiling and stirring for approximately 2 minutes. Remove pan from heat.
6. Stir in the vanilla extract. Gently press a piece of plastic wrap directly against the surface of the cream filling to make sure that a skin doesn’t form; chill the filling mixture in the refrigerator for a minimum of 1 hour.
7. In a small chilled metal or glass bowl, using a hand mixer with chilled beaters, beat the heavy cream until stiff peaks form. Fold the beaten cream into the chilled cream filling.
8. For frosting, in a small saucepan, over low heat, combine remaining 1/2 cup milk and the chocolate pieces; stir until smooth. Remove from heat; stir in chilled margarine, a little bit at a time, until smooth. Pour into a bowl; let stand until firm enough to spread, about 1 hour.
9. Using a long serrated knife, trim cake tops if necessary to make layers; slice layers horizontally in half. Place one layer, cut side up, on a serving plate. Spread layer with 1/3 of the filling and top with 1/3 of the banana slices; top with second layer. Repeat procedure ending with top layer.
10. Carefully run a metal spatula around the sides of the cake to smooth the cream filling. Using even strokes, cover the sides and top of the cake with the chocolate frosting. Serve immediately or chill until ready to serve.