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Once the cake has been removed from the oven, increase the heat to 200C/180C fan/gas 6. Leave the cake in its tin. Put the sugar cubes in a large bowl and crush with the end of a rolling pin to a sugary rubble. Mix in the preserving sugar, pearly balls and egg white – it should have the texture of wet sand. Tip the mixture on top of the cake and level the surface. Bake the cake for 5 mins to set the sugary crust, then remove and leave to cool.
Once completely cooled, remove from the tin and peel off the baking parchment. Sprinkle the top with edible glitter, tie ribbons around the side and decorate with your favourite figurines, if you like.