Cut the dark chocolate couverture into large pieces and melt with the oil in a saucepan over a warm water bath over low heat.

Mix the milk, egg and yoghurt with a whisk. Peel the bananas and cut into small cubes. Mix the flour, cocoa powder, cane sugar and baking powder in a bowl. Carefully fold in the banana cubes, then stir in the milk-yoghurt-egg mixture Add the oil mixture and mix briefly with a wooden spoon. Preheat the oven to 180 degrees.

Line the hollows of the muffin sheet with silicone muffin molds. Spread the muffin dough over the molds and bake in the oven for 20-25 minutes. Allow to evaporate in the mold for 5-10 minutes. Roughly chop the hazelnuts. Put cocoa powdered sugar in a cup with water Mix until smooth, brush onto the banana-chocolate muffins with a brush and sprinkle with the hazelnuts. Let the muffins cool on a wire rack.