In a large mixing bowl whisk together the eggs and sugar then add the mashed banana. Sift in the flour, baking powder, bicarbonate of soda, cinnamon and ginger. Pour in the melted butter and mix until smooth. Spoon a large tablespoon into fourteen muffin cases. Sprinkle over the fudge chunks, pushing them down into the mixture a little with a spoon.
Bake in preheated oven for 25 minutes until a skewer inserted into the centre comes out clean.
Spread a little of the melted chocolate onto the tops of the muffins and allow to cool.