Preheat and Prep: First, preheat your oven to 200°C (180°C fan). Line a 12-hole muffin tin with paper cases.

Combine Dry Ingredients: In a large mixing bowl, add the plain flour, sifted cocoa powder, caster sugar, light brown sugar, baking powder, bicarbonate of soda, and salt. Use a whisk to combine everything thoroughly, ensuring there are no lumps of brown sugar.

Mix Wet Ingredients: In a separate medium bowl or large jug, whisk together the egg, buttermilk, vegetable oil, and vanilla extract until they are just combined.

Combine Wet and Dry: Pour the wet ingredients into the bowl of dry ingredients. What works best for me is using a rubber spatula to fold the mixture together. Stop as soon as you can no longer see streaks of dry flour. The batter should be thick and a bit lumpy – this is perfectly normal and desirable!

Fold in the Chocolate: Gently fold in about two-thirds of your chopped dark chocolate. Be careful not to overmix at this stage.

Fill the Cases: Divide the batter evenly between the 12 prepared muffin cases. They should be about three-quarters full. Sprinkle the remaining chopped dark chocolate over the top of each muffin.

Bake the Muffins: Place the muffin tin in the preheated oven and bake at 200°C (180°C fan) for 5 minutes. Then, without opening the oven door, reduce the temperature to 180°C (160°C fan) and continue to bake for another 15-17 minutes.

Check for Doneness: The muffins are ready when they are well-risen, springy to the touch, and a skewer inserted into the centre of one comes out clean (you might hit a melted chocolate chunk, so test in a couple of spots!).

Cool Down: Let the muffins cool in the tin for about 5 minutes before carefully transferring them to a wire rack to cool completely. They are incredible when still slightly warm.