What you need:
1. Preheat oven to 180°C/280°F/ Gas 4. Line a 12 hole muffin tin with paper cases.
2. Put the flour, sugar and bread soda into a bowl and mix well.
3. In a separate bowl beat the mashed bananas, peanut butter, milk, vinegar, oil and vanilla.
4. Add the dry ingredients to the beaten ‘wet’ mixture and gently stir to combine.
5. Fill the muffin cases with a tablespoon of mixture for each muffin. Top each one with a half a teaspoon of Nutella and swirl it with a cocktail stick or knife.
6. Bake for about 15 minutes until risen and golden brown.
7. Remove from the oven and leave in tin for 5 minutes, then transfer to wire tray to cool completely before storing.