Preheat the oven to gas 4, 180°C, fan 170°C. Line a 12-hole muffin tin with muffin cases.
In a large bowl, put the butter, sugar, flour, eggs and milk, then whisk with an electric hand-whisk on a medium speed for 1 minute.
Divide the mixture between 2 bowls and stir the cocoa powder into one of the mixtures. Using a teaspoon, take small dollops of each cake mixture and spoon them alternately into the muffin cases. Using a skewer or the end of a teaspoon, mark a cross a couple of times right through the mixture to create the marbling.
Bake for 25 minutes. Remove from the oven and leave in the tin for 5 minutes, before transferring to a wire rack to cool.
Whisk the frosting ingredients together. Spread the mixture onto the cupcakes. Decorate with chopped Maltesers and strawberries.
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As seen in Real Food magazine