1. Preheat the oven to 180°C, fan 160°C, gas 4. Place the paper cupcake cases in the 12-hole muffin tin.
2. In a large mixing bowl, use an electric hand whisk to cream together the butter, sugar and vanilla extract until light and fluffy. Beat in the eggs one at a time, adding a little flour with each egg to stop the mixture splitting. Sift over the remaining flour and baking powder, then gently fold in with a wooden spoon until the mixture is smooth. Stir the milk into the cake mixture, then divide three-quarters of it equally between 9 cupcake cases. Stir the cocoa powder into the rest of the mixture, then spoon into the last 3 cupcake cases. Bake all the cakes for 25 minutes until risen and a skewer inserted into the centre comes out clean. Cool on a wire rack.
3. Peel the paper cases off the cupcakes. Halve the vanilla cakes horizontally for the burger buns and cut each of the chocolate cakes into 3 horizontally to make 9 burgers. Brush the domed tops of the vanilla cake halves with the apricot glaze, then scatter the coloured sprinkles over to resemble seeds.
4. Dust a surface with icing sugar and roll out the yellow and green icings to 3mm thick each. Using a 6.5cm round cutter, stamp out 9 circles from each colour.
5. To make the cheese, gently flatten the yellow icing circles around the edges with your fingers and put to one side. Roll the end of a cocktail stick around the edges of the green circles to create a crinkled effect for the lettuce.
6. To make the buttercream, in a large mixing bowl, use an electric hand whisk to beat together the butter and vanilla extract for 2-3 minutes, until pale and soft. Add half the icing sugar and beat on a low setting at first, so the icing sugar doesn't puff up and out of your bowl. Beat on a higher setting until smooth, then repeat with the rest of the icing sugar. Continue to beat for 1-2 minutes, until pale and fluffy. To colour the buttercream, beat in a little food colouring. If you're using liquid food colouring, take care not to add too much as it will make the buttercream looser. If you want a deeper colour, it's better to use food colourings in gel or paste form.
7. Spread the bottom halves of the Victoria sponges with a little buttercream and top with 'lettuce'. Add more buttercream and top with a 'burger', then more buttercream and a slice of 'cheese'. Pipe red 'ketchup' on each, using the writing icing pen, finish with the vanilla cake 'bun' tops and serve.

Cook's tip: if you are piping buttercream rather than using it as a filling or topping, loosen the mixture with a couple of teaspoons of milk.