Ingredients
250g plain flour 
1 tsp bicarbonate of soda
1 tsp baking powder 
35g malted chocolate drink such as ovaltine or milo or cocoa powder 
90g soft brown or light muscovado sugar
5 mars bars (just under 200g), chopped into pieces 
300ml sour cream
2 eggs 
½ tsp vanilla extract
90g butter  

Method
Heat your oven to 180c and line a muffin tray with muffin cases (muffin trays are deeper than the traditional fairy cake trays, if you only have a fairy cake tin then ensure you buy fairy cake cases and you will get closer to 30). 

To a large bowl add the flour, bicarb, baking powder, chocolate powder, sugar and mix together gently.

In a jug put the sour cream, eggs, vanilla and melted butter and mix.

Add the wet ingredients to the dry and gently fold.  To do this get a large metal spoon, put into your mix, scrape around the edge and then cut through the middle.  Repeat this process until the flour is just incorporated - don’t over mix or they will not be as light. Add your chopped up mars bar and give a careful few stirs to mix through.

The easiest way to get your batter into the paper cases is with an ice cream scoop or ¼ cup.  You want each case to only be ¾ full - they will rise and fill the cases.  If you overfill they will spill over.  Place into the oven and bake for around 20 minutes.  I say around - different ovens cook slightly differently so check at 18 minutes and again every 2 minutes until they are done. 

To test you need to insert a tooth pick or skewer in to the middle of the muffin and it should come out clean, that means with no raw batter on it stick - crumbs are fine.