Lightly crush the Saffron and cover with the water. Allow to stand for 2 hours or overnight.
Pre-heat the oven to 170°C, 325°F, Gas Mark 3.
Grease and line a deep 18cm (7") cake tin. Cream the butter and sugar together. Beat in the eggs, adding a little flour if necessary. Strain the Saffron liquid and discard the strands. Gently fold half the flour into the cake mixture, followed by the Saffron liquid. Fold in the remaining flour and stir in the currants. Transfer to the prepared tin and cook for 1½ - 1¾ hours or until well risen and firm to the touch.
Allow to cool slightly before turning out. When cold, split the cake in half. Blend together the cream cheese, milk and icing sugar and fill the cake with 2/3 of this mixture. Use the remainder to decorate the top of the cake together with the strips of lemon rind. Dust with icing sugar before serving.