Preheat the oven to 190°C/375°F/gas mark 5. Put the cream or milk and the saffron into a small saucepan, bring just to bubbling point and then leave to cool, stirring once or twice so that the saffron infuses well. Beat the butter and icing sugar together until soft, then beat in the saffron cream — make sure no saffron strands are left on the beater or spoon. Stir the flour, semolina and currants into the mixture with a wooden spoon. Using floured hands, gather the dough into a ball. Roll out on a floured board until it is 5 mm/¼ level in thick and cut into rounds with a pastry cutter. Place on lightly buttered baking sheets and bake for 8-10 minutes, until pale brown. Leave to cool on the baking sheets.