Preheat your own to 200C (400F). Butter a 12 hole muffin tray generously and set aside.

In a large bowl, whisk together the flour, sugars, baking powder, baking soda, salt and cocoa powder. Once they are combined, add in the chocolate chunks, stir to combine, and set the bowl aside.

In a medium sized bowl, whisk together the egg, buttermilk, oil and vanilla extract. Pour the wet ingredients into the bowl of dry ingredients and mix until just combine, being careful not to over mix.

Fill each of the muffin tray slots half way with the batter, and spoon 1 -2 generous teaspoons of Nutella into the centre of each slot. Then pour the remaining batter over the top of each muffin tray slot, ensuring you use up all batter and cover the Nutella completely.

Bake in the oven for 15-20 minutes, or until a toothpick inserted off centre (to avoid the Nutella) comes out clean. Once the muffins are ready, remove from the oven and allow to cool for 10 minutes in the pan. Then transfer to a wire rack to cool completely.