Start by making the buttercream. Beat the softened butter in a bowl with a beater for 5 minutes till pale. Slowly mix in the vanilla and icing sugar and continue beating for at least another 5-6 minutes until light and fluffy. Add in your food colouring and mix. Use the buttercream to fill the 2 x 12cm sponges to make a small cake and coat the top and edge too. Flatten out with a palette knife and chill for 15 minutes to harden. When ready, decorate the top with piped buttercream, sprinkles and a `mum` sugar plaque. Do the same with the cupcakes. Place a sheet of tissue paper under the small cake and lift into the box. Place in the decorated cupcakes and close the box. Tie up with a ribbon and the gift box is ready.