Preheat the oven to 180C/350F/Gas 4 and line a 12-hole cupcake tins*2 with paper cases.

Cream the butter and sugar together in a bowl until pale. Beat in the eggs a little at a time.

Fold in the flour using a large metal spoon, Take a separate (smaller) mixing bowl, and pour half of your mixture into the first mixing bowl, add the teaspoon of vanilla extract and mix well.

In the second mixing bowl, pour another half of your mixture and add the 60g of dark chocolate powder and mix well.

Once your two mixtures are ready, spoon a teaspoon of vanilla mixture into each cupcake case, then follow with a spoon of chocolate mixture. Repeat until each cupcake case is half full.

For the buttercream icing, beat the butter in a large bowl until soft. Add half the icing sugar and beat until smooth

Then add the remaining icing sugar with one tablespoon of the milk, adding more milk if necessary, until the mixture is smooth and creamy.

Take a separate (smaller) mixing bowl, and pour half of your buttercream mixture into the first mixing bowl, add the teaspoon of vanilla extract and mix well.

In the second mixing bowl, pour another half of your buttercream mixture and add the 30g of dark chocolate powder and mix well

Spoon the icing into a piping bag with a star nozzle and pipe the icing using a spiralling motion onto the cupcakes in a large swirl.