1. Preheat the oven to 350°F (180°C). Line a muffin tin with paper liners and set aside. Chop the walnuts for the batter and decoration – the ones for the batter a bit coarser, the ones for the decoration quite finely. Set aside.

2. Add the sugar and butter to a large bowl and mix until light and fluffy. Add the egg and vanilla extract and mix until well combined. Mash the bananas and add to the bowl – mix until well combined. In a second bowl mix the spelt flour with baking powder and salt. Add together with the milk to the large bowl and mix until just combined (with a spatula, for example). Add the chopped walnuts and fold in. Divide the batter between the paper liners. Sprinkle with the finely chopped walnuts and sugar and bake for 20-22 minutes or until a toothpick inserted into the center of a muffin comes out clean. Take out of the oven and let cool down on a wire rack.