Heat the oven to 356°F (180 °C). In a pot, pour the milk and add the butter. Bring to a boil and remove from the heat. Stir and cool.
Whisk the eggs in a large bowl. Add the mashed bananas. With the mixer on low speed, mix the dough, twice, alternately adding flour and milk mixture.
Grease the muffin forms or lay them out with paper baskets. Distribute the dough into them and fill them up to 2/3 of their volume.
Cover with the frozen wild berries. Bake the cupcakes for 25 minutes.