Coarsely chop the couverture and coconut oil, put half of it in a bowl and melt it on a not too hot water bath. Take off, stir in the rest of the couverture and stir until smooth. When the couverture feels cool to the touch, but is still liquid, it has the right temperature.
Cut the banana into medium-sized pieces and dip them in the chocolate coating. Drain, place on baking paper and leave to dry. Put the rest of the couverture in a small freezer bag, cut off a small tip and decorate the banana pieces as you like.
Pour the milk into a tall, narrow container, add the cream powder and whisk with a hand mixer for approx. 3 minutes. Pour the cream into a bowl and chill for approx. 10 minutes. Serve the cream with chocolate bananas and decorate with mint.