Prepare Your Tin: Preheat your oven to 190°C (170°C fan) and line a 12-hole muffin tin with paper cases.

Combine Dry Ingredients: In a large bowl, whisk together the plain flour, baking powder, bicarbonate of soda, salt, caster sugar, and light brown sugar. Mixing them thoroughly now ensures an even rise later.

Mash the Bananas: In a separate medium bowl, mash the ripe bananas with a fork until they are mostly smooth. A few small lumps are perfectly fine.

Mix Wet Ingredients: To the bowl with the mashed bananas, add the eggs, vegetable oil, and vanilla extract. Whisk everything together until it's well combined.

Combine Wet and Dry: Pour the wet banana mixture into the large bowl of dry ingredients. What works best for me is using a rubber spatula to gently fold the ingredients together. Stop as soon as you can no longer see big streaks of flour. Remember, a lumpy batter is your friend!

Fill the Cases: Divide the batter evenly between the 12 paper cases. An ice cream scoop is a great tool for this, as it helps keep the portions consistent. They should be about three-quarters full.

Add the Nutella: Add a heaped teaspoon of Nutella to the top of the batter in each muffin case.

Create the Swirl: Take a cocktail stick or a small skewer and gently swirl the Nutella into the top of the batter. The idea for this finishing touch came from watching a pastry chef in Florence; it looks so inviting and ensures you get Nutella in every bite. Two or three swirls are plenty – you want distinct ribbons, not a completely mixed-in effect.

Bake to Perfection: Bake in the preheated oven for 18-22 minutes. You can check if they're done by inserting a skewer into the cakey part of a muffin (avoid a Nutella swirl). If it comes out clean, they're ready.

Cool Down: Let the muffins cool in the tin for about 5 minutes before transferring them to a wire rack to cool completely.