To make the cake: Preheat the oven to 350° F. Line a baking sheet with parchment paper. Butter the paper and dust lightly with flour, tapping out the excess.
Sift together the flour, baking powder and cocoa. In the bowl of an electric mixer, combine the butter and sugar and beat on medium-high speed until creamy. Add the eggs one at a time, beating well after each addition. Add the dry ingredients and blend well. Spoon the batter onto the prepared pan, smooth the top with a rubber spatula and bake about 20 minutes, until a wooden pick inserted in the center comes out clean. Let the cake cool in the pan, set on a wire rack, for 10 minutes. When the cake is cooled, cut enough rounds to cover the bottom, sides and tops of four individual 6-inch round molds. The cake can be made up to 3 days ahead; if baked ahead, store, covered loosely in plastic wrap, in a cool dry place until time to use.
To make the banana mousse: In a small bowl sprinkle the gelatin over the banana rum and let rest for 5 minutes. Place this mixture over hot water in the top of a double boiler and heat until it melts.
In the bowl of a food processor, purée the bananas. Gradually add the puréed bananas to the gelatin.
In the well-chilled bowl of an electric mixer fitted with a chilled balloon whip, beat the heavy cream on high speed about 1 minute, until peaks just begin to form. With the mixer on low speed, add the sugar and whip about 2 minutes until soft peaks form. Be careful not to over-whip or the mousse will be grainy. Add the whipped cream to the bananas, gently folding in the cream 1/2 cup at a time.
To make the ganache: In a medium saucepan combine the cream and corn syrup and bring to a boil over medium heat. Remove the pan from the heat and add the chocolate pieces, stirring until the chocolate is melted and the mixture is smooth and shiny.
To make the orange foster caramel sauce: In a medium saucepan bring the sugar and water to a boil over medium heat. Cook 8 minutes, or until the mixture reaches a light brown color and a caramel is formed. Remove the pan from the heat, add the Grand Marnier, orange juice, lemon juice and butter, and return the mixture to the stove. Bring to a slow boil over low heat and cook 1 minute, until the mixture becomes liquid again.
To make the puff-pastry rounds: Preheat the oven to 350° F. Grease a large sheet pan with softened butter.
With a rolling pin, roll the puff pastry into eight 4-inch-diameter thin rounds and place on the prepared pan. Cover the pastry with a second clean cookie sheet to prevent the pastry from rising. Bake 5 minutes, or until golden. Remove the pastry from the oven and allow to cool. Top each round with 5 banana slices and sprinkle with 1 tablespoon of sugar. Place the pastry rounds under the broiler for 3 to 4 minutes, until the sugar just begins to caramelize.
To assemble: Line the bottom and sides of the molds with the cake rounds. Sprinkle the cake rounds with 1 tablespoon of Grand Marnier; do not soak them. Fill the molds with the banana mousse, placing it inside the cake shells. Place a final piece of cake on top of the mousse, sprinkling again with Grand Marnier. Refrigerate the molds about 30 minutes, or until set. Unmold the individual molds by turning upside down onto a rack set over waxed paper. Pour the chocolate ganache over the "bombes" until completely covered. Refrigerate 45 minutes to 1 hour, until set.
To serve: Cut the bombes in half. Place one half on each dessert plate. Pour 1/4 cup of orange-foster sauce around each bombe. Place a scoop of ice cream beside each. Place a banana-topped puff-pastry round beside each serving.
Garnish with 2 strips of orange zest and a mint sprig.Makes 6 to 8 Source: