Preheat your oven to 180°C (160°C fan) and line a 12-hole muffin tin with paper cases. The oven should be fully up to temperature before the batter goes in—this ensures a quick rise and a domed top.

Mash the bananas in a large mixing bowl using a fork or potato masher until they form a smooth, almost liquid paste with only a few small lumps remaining. You should see a glossy, wet puree that smells intensely fruity.

Add the wet ingredients: To the mashed bananas, stir in the peanut butter, melted butter, brown sugar, eggs, vanilla extract, and milk. Whisk everything together until the mixture is uniform and pale tan in colour—it should look like a thick, smooth sauce with a rich, nutty aroma.

Combine the dry ingredients in a separate small bowl: the flour, bicarbonate of soda, baking powder, and salt. Whisk them together to aerate and distribute the raising agents evenly.

Fold the dry into the wet: Gently tip the flour mixture into the banana mixture and fold with a spatula. Stop as soon as you see no more streaks of white flour—the batter will look slightly lumpy and thick. Overmixing will make the muffins tough, so a few small lumps are absolutely fine.

Add the chocolate chips (if using) and fold them in gently. You'll hear the soft clink of chips against the bowl and see them evenly dispersed through the batter.

Divide the batter evenly among the 12 paper cases. Each case should be about three-quarters full—the batter will be thick and slightly sticky, so use two spoons or a cookie scoop. The tops should look slightly domed and glossy.

Bake for 16-18 minutes, rotating the tin halfway through. The muffins are done when they're golden brown on top, spring back lightly when touched, and a skewer inserted into the centre comes out clean. You'll smell the warm peanut butter and banana filling your kitchen.

Cool in the tin for 5 minutes, then transfer to a wire rack. The muffins will be very soft and fragile straight from the oven, so let them firm up in the tin first. Once on the rack, they'll release steam and develop a slightly crisper outer edge.