Lubricate with butter (1 tbsp.spoon) molds for banana mini-muffins and preheat the oven to 180 degrees.
Cut nuts and place in a bowl with sugar, flour and cinnamon. Stir and add a slice of butter. It is best to mix the oil with a fork. Leave it aside for now.
Place the peeled bananas in a deep bowl. Add sugar, egg and vanilla extract. Whisk well with a whisk.
Grind the chocolate and add it to the dough. In a separate bowl, mix the flour with baking soda, salt and baking powder.
Add this mixture to the banana. Mix well again, distribute the dough into baking tins and place in the oven for 10-15 minutes.