1Pre-heat the oven to 180C/160C Fan/Gas 4. Grease an ovenproof 1L pudding basin. Line the base with baking paper.
2Put 115g butter, 115g caster sugar, 2 eggs, 115g flour and 1/2tsp baking powder in a bowl. Beat for 2-3 minutes with an electric hand-whisk, until pale and fluffy. Set aside.
3In another bowl, beat the 60g butter, 60g sugar, 1 egg, 40g flour and 1/2 level tsp baking powder, plus 25g cocoa powder and 1 tbsp milk.
4Put alternate spoonfuls of the two mixtures in the pudding basin. Level the surface. Bake for 45-55 minutes, until risen. To check if it's ready, insert a skewer into the centre; it should come out clean.
5Cool in the basin on a wire rack for 15 minutes. Turn out and leave to cool completely.
6Put the fairy cake cases in a bun tin. Put the remaining caster sugar, eggs, flour and baking powder, plus 115g butter, in a bowl. Beat for 2-3 mins, until light and creamy. Divide the mixture between the paper cases.
7Bake for 15 minutes, or until risen and golden brown the tops should spring back when lightly pressed. Leave to cool on a wire rack.
8Beat together the rest of the butter, icing sugar and vanilla, until light and fluffy. It's best to use an electric hand-whisk for this.
9Stand the marble cake, rounded-side down, on a plate. Trim off the edges of the top third of the cake to make a dome shape.
10Spread over enough of the buttercream to cover.
11Divide the remaining buttercream into two equal portions. Colour one pale pink using 3-4 drops of the pink food colouring.
12Fit a piping bag with a star nozzle. Spoon the buttercream into the bag with the cream-coloured half on one side and the pink on the other. This gives a two tone effect when piped.
13Starting in the centre, pipe a spiral of buttercream on top of each cupcake.
14Stick the chocolate finger biscuits, lengthways, all along the base of the cake.
15Push a cocktail stick into the base of each fairy cake through the paper case. Push the other end into the top of the marble cake, to secure. Use the other cupcakes to cover the rest of the iced sponge (make sure there are no cocktail stick points poking out).
16Tie a ribbon around the base and secure with a bow.