Heat a nonstick saute pan over medium to low heat. Add the butter and brown sugar to melt. Place the banana halves in the pan and saute until the bananas caramelize, approximately 1 minute. Turn the bananas over and caramelize on other side. Remove the pan from the heat. Put the sugar, whipping cream, and vanilla extract in a metal bowl and whisk until firm peaks form. To serve, grate the dark chocolate on a plate. Sift the icing sugar over the prepared brownies and plate. Place the caramelized bananas on the plate and dollop the whipping cream mixture on the brownie.