Preheat the oven to 190°c. Line a muffin tin with paper cases or put 12 silicon muffin cups on a baking sheet.
In a large bowl, mix together the flour, baking powder, cinnamon, cocoa powder and sugar.
In another bowl mix the melted margarine and almond milk.
Mash the bananas, the add the eggs and the vanilla. Add the milky mixture and combine.
Add the wet ingredients to the dry ingredients and mix well.
Fold in the chestnut & chocolate pieces.
Transfer the batter into the muffin cases.
Bake the muffins for about 25 minutes, until light brown and an inserted skewer comes out clean.
Cool them for a few minutes in the tin or silicon cases, then transfer them onto a wire rack to cool completely.