Preheat the oven to 175°C. Butter a loose bottomed 22cm diameter cake tin and line the bottom with baking paper.
Beat the butter, sugar and the finely grated zest from 2 oranges until pale, thick and fluffy. Add the eggs one at a time, beating well after each. Stir in the flour and ginger, making sure they are mixed in thoroughly but not beaten.
Pour the mixture into the cake tin, place in the oven and bake for 45-55 minutes or until a skewer inserted into the middle of the cake comes out clean. Remove from the oven and cool completely then remove from the tin.
Put the orange juice, icing sugar and cream cheese into a bowl and beat until smooth. Spread this all over the cake. Decorate with slices of ginger and the remaining orange zest. Serve in wedges.