1: Preheat the oven to gas 4, 180ºC, fan 160ºC. Line a 12-hole muffin tin with cupcake cases.
2: Cream the butter and sugar until pale and fluffy. Gradually add the eggs, beating well between each addition. Stir through the orange juice and zest. Sift in the flour, baking powder and cocoa. Gently fold through until fully combined.
3: Divide the mixture evenly between the cupcake cases. Bake for 20 mins, or until well risen and firm on top. Remove from the tin and leave to cool on a wire rack.
4: To decorate, spoon the vanilla frosting into a piping bag. Pipe in a swirling motion on top of the cupcakes – leaving a small gap in the centre. Fill each gap with ½ tsp of marmalade, then insert the Jaffa Cake halves into the topping to look like butterfly wings. Scatter with the orange zest before serving.