Preheat the oven to 180°C (356°F).
Mash the banana.
In a bowl, mix the mashed banana, whole wheat flour, baking powder, sugar, and salt.
Cut cold butter into the mixture and combine with the dough.
Gradually add milk while kneading until the dough is moist.
Shape the dough into rounds and place on a pan.
Bake in the oven at 180°C (356°F) for 20-25 minutes.