Preheat the oven to 170°C fan/375°F/gas 5. Grease and line three 20cm sandwich cake tins. Place the butter, sugar, treacle and golden syrup into a large bowl, then beat with an electric mixer (I prefer the free-standing type) for 5 to 7 minutes, or until light and fluffy. Crack in the eggs one at a time, whisking well before adding the next – if the mixture starts to split, whisk in 1 tablespoon of the flour. Sift in the ground ginger, cinnamon and flour and fold through, then stir in the soured cream. Strain the ginger syrup into a bowl and set aside, chop the ginger into 0.5cm pieces, then stir them into the cake mixture.
Equally divide the mixture between the prepared cake tins, smoothing it out with a spatula. Bake the cakes for 25 minutes, or until an inserted skewer comes out clean, then turn them out on to a wire cooling rack and leave to cool.
Meanwhile, make the icing. Beat the butter and cream cheese with an electric mixer for 2 to 3 minutes, or until pale and smooth. Sift the icing sugar into a large bowl, then add to the butter mixture in two stages, beating well between each until beautifully smooth – if the mix seems too loose, add a little more icing sugar until the consistency is just right.
Once the cakes have cooled, use a sharp serrated knife to trim the tops off them to make the surfaces nice and flat. Generously brush some ginger syrup over a flat round and spread with some of the cream cheese icing. Layer over another sponge, top with another layer of ginger syrup and icing, then finish with the remaining sponge. Use a palette knife to smooth the sides and the top of the cake with the rest of the icing, finish with an extra drizzle of ginger syrup, et voilà!
I sometimes like to sprinkle the top with crushed ginger biscuits and extra pieces of stem or crystallised ginger, or even get creative and decorate the edges like I’ve done in the picture, but it’s up to you. Go nuts!