1. Preheat the oven to 350°F (180°C). Line a standard loaf tin* with baking parchment and grease lightly. Set aside. Melt the butter and let cool down. Add the milk and vinegar to a small bowl and let sit for about 5-6 minutes.

2. Add the bananas to a bowl and mash. Add the sugar (or xylitol), melted butter, milk vinegar mix, eggs, and vanilla extract – mix until well combined. Mix the flour, baking powder, cinnamon, cardamom, and salt. Add to the bowl with the bananas and mix until just combined. Add the blueberries and chopped walnuts and fold them in. Pour the batter into the loaf tin and smooth out the top. Sprinkle with some more chopped walnuts and bake for 50-60 minutes or until a wooden skewer inserted into the center comes out clean. Take out of the oven, remove the cake from the baking tin, and let cool down completely on a wire rack.