Preheat the slow cooker if necessary; see the manufacturer's instructions. Butter a soufflé dish that is 14 cm (5½ inches) across the base and 9 cm (3½ inches) high and base-line with a circle of nonstick baking paper.
Put the measured butter, sugar, syrup and dates into a saucepan and heat gently, stirring, until the butter and sugar have melted. Take the pan off the heat, add the flours, bicarbonate of soda, ground and chopped ginger, eggs and milk and beat until smooth. Pour into the lined dish and cover the top loosely with buttered foil.
Lower the dish carefully into the slow cooker pot on foil straps (see
Take the dish out of the slow cooker pot, leave to stand for 10 minutes, then remove the foil and loosen the edge of the cake with a knife. Turn out on to a wire rack, peel off the lining paper and leave to cool.
Sift the icing sugar into a bowl and mix in just enough water to make a smooth, thick icing. Spoon over the top of the cake, then decorate with the strips of ginger. Leave to set. Cut into wedges to serve.