gel or paste food dyes in blue, green, yellow, orange and black
icing sugar, to dust
Heat the oven to 180C/160C fan/gas 4. Grease and base-line 3 x 20cm sandwich tins. Beat the butter and sugar together until light and fluffy then briefly beat in the vanilla. Slowly add the egg beating between each addition. Fold in the buttermilk then sift and fold in the flour in three additions. Fold in the milk. Divide the batter between the sandwich tins.
Bake in the oven for 20-25 mins until golden, risen and a skewer inserted into the middle comes out clean. Leave in the tins for 5 mins then turn out onto wire racks to cool completely.
To make the buttercream beat the butter until soft with an electric hand whisk or in a table top mixer. Sieve in the icing sugar then beat for 10 mins until pale and fluffy. Briefly beat in the vanilla, orange extract (if using) and the milk.
To assemble put a blob of buttercream on a 25cm cake board or serving plate. Put one of the sponges onto the plate then spread with a layer of buttercream and half the jam. Top with a second sponge and spread again with buttercream and the remaining jam. Top with the third sponge then cover the top and sides of the cake with the remaining buttercream, smoothing the edges with a palette knife. Chill in the fridge for 30 mins.
Dye 700g of the fondant icing a rich blue. Lightly dust a work surface and rolling pin with icing sugar. Roll the blue icing into a circle large enough to cover the top and sides of the cake. (Keep any off cuts for making bubbles). Mould Duck’s body and wings from white fondant and cut ovals of white for his eyes. Dye some fondant a green/blue colour to make Duck’s head. Dye small amounts of fondant, yellow, orange and black for his beak, feet and eye details. Use a little water to stick all the parts together.
Dye the remaining fondant in shades of pale blue and roll into balls to make bubbles. Cover the cake with the bubbles, again using a little water to help stick them on. The cake will keep well for 3 days.