With the rack in the middle position, preheat the oven to 180 °C (350 °F). Line a 23 x 13-cm (9 x 5-inch) loaf pan with a strip of parchment paper, letting it hang over both sides. Butter the other two sides.
In a bowl, combine the flour, baking powder, and baking soda. Set aside.
In another bowl, cream the butter with the brown sugar, cocoa powder, and vanilla with an electric mixer. Add the eggs, one at a time, and beat until smooth.
On low speed, add the bananas and dry ingredients alternately with the milk. Add the chocolate and combine. Pour into the prepared pan and sprinkle with the peanuts.
Bake for about 1 hour or until a toothpick inserted in the centre comes out clean but slightly topped with melted chocolate. Let cool for at least 1 hour and unmould. Serve warm or cold.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.