Preheat the slow cooker if necessary; see the manufacturer's instructions. Check that a 1.5 litre (2½ pint) pudding basin will fit inside your slow cooker pot with a little room to spare, then butter the inside of the basin and base-line with a circle of nonstick baking paper.
Put the dried fruit, nuts, ginger and grated apple into a large bowl. Add the fruit rinds and juice and brandy and mix together well. Stir in the remaining ingredients. Spoon into the buttered basin, pressing down well as you go. Cover with a large circle of nonstick baking paper, then a piece of foil. Tie with string and add a string handle.
Lower into the slow cooker pot, using foil straps (see
Cover with fresh foil, leaving the baking paper in place. Retie with string and keep in a cool place for 2 months or until Christmas.
When ready to serve, preheat the slow cooker if needed, add the pudding and boiling water as above and reheat on high for 2–2½ hours. Remove the foil and paper, loosen the pudding and turn out. Warm the brandy in a saucepan, if using. When it is just boiling, flame with a taper and quickly pour over the pudding. Serve with brandy butter or cream.