Preheat the oven to 220°C /430F/Gas Mark 7. Line a 12 cup muffin tin with cupcake liners.
Roughly chop the walnuts and chocolate bar (if not using chips), and set them aside. Mash the bananas using a fork or potato masher and set them aside.
Add in the flour mixture, walnuts, chocolate chips and mashed bananas. Fold together until just mixed.
Divide the batter into the 12 cupcake liners. Top with a teaspoon of cinnamon sugar (optional extra), and bake at 220°C /430F/Gas Mark 7 for 5 minutes. Turn down the oven to 200°C/390F/Gas Mark 6 and bake for a further 12 to 15 minutes, until just baked and a toothpick or cake tester comes out mostly clean.
Allow the muffins to cool on a cooling rack before serving.
All temperatures stated are for conventional ovens. Decrease the temperature by 20°C/25°F or gas mark 1 for "fan" or air-fryers.
Notes
All ingredients should be at room temperature and the butter should be softened.
Making a Banana Chocolate Chip Muffin Bread/Loaf
If wanting to make bread or loaf from this recipe, simply grease and line a regular size loaf tin. Preheat the oven to 180°C or 160°C fans assisted. Follow the instructions to make the batter.Pour the batter into the loaf tin, sprinkle with the cinnamon sugar, and bake for 50 to 60 minutes or until a cake tester comes out clean from the centre. Allow the banana bread to cool for at least 15 minutes before removing it from the loaf pan and allowing it to cool completely before serving.For fan-forced or fan-assisted ovens decrease the temperature by 20°C/25F.