Once the cakes are completely cooled, ice each layer, adding jam in the middle, then crumb coat the cake and chill in the fridge for 30 mins.
Ice the cake with another layer of buttercream, smooth the sides using a cake scraper. Return to the fridge for 1 hour.
To make the white chocolate ganache, heat the cream slowly in the microwave and pour over the chocolate, stir until combined. Take the cake out the fridge and pour the ganache on top and down the sides of the cake. Put back in the fridge to set then paint the ganache drip with the edible gold lustre dust using the same method as the cookies.
Stick the crown cookies around the side of the cake using left over ganache, decorate the top with berries and a cookie crown.