Preheat oven to 400 degrees F. Brush a sheet of filo pastry lightly with butter. Fold filo as you would a letter. Place banana at the bottom end of the folded filo sheet, and then roll. Place on a non-stick or parchment paper-lined baking sheet. Repeat this process with remaining bananas. (Leftover filo pastry can be tightly wrapped and stored in the fridge, up to 2 weeks, for later use). Bake bananas in the middle of the oven 15-20 minutes, or until the filo is golden brown.
While this occurs, place cream in a pot and bring to a simmer. Whisk in chocolate and stir until it is melted and well incorporated into the cream. Pour a small pool of sauce onto 4 dessert plates. Cut bananas in half at a 45 degree angle and arrange on the plates. Garnish with a scoop of ice cream and a sprig of mint.