Preheat the oven to 190C/375F/gas 5. Butter each hollow in a muffin tin or line them with paper cases.
Sift the flour with the cocoa powder, baking powder and the bicarb of soda into a large bowl, stir in the sugar making sure you get rid of any lumps. Add the chocolate chips to the flour mix.
In another bowl beat the egg with the buttermilk, vanilla extract and the oil until well combined.
Fold the wet ingredients into the dry mix only until just combined, don’t over mix.
Spoon the mixture into paper cases – this will make 12 large muffins. Sprinkle with pearl sugar, if using.
Bake for 20 minutes. Leave in the tin for 5 minutes, then remove and cool on a wire rack.
