Combine the mixed fruit, prunes, muscovado sugar, rum and stout in a mixing bowl. Stir well to mix, cover and leave for 24 hours to soak.
After 24 hours, mix the walnuts, almonds, ground almonds, breadcrumbs, flour, butter, spices, cherries and eggs along with the soaked fruit mixture in a large mixing bowl, making sure you include all the soaking liquor from the soaked fruit. Mix well until completely combined (let all the members of the family have a stir and make a wish).
Cover with cling film and leave to stand in a cool place for 24 hours.
After 24 hours, grease a 1.2 litre/2 pint pudding basin with butter. Cut a circle of baking paper and place into the bottom of the pudding basin and then grease it with a little more butter. Pack the pudding mixture into the pudding basin, pressing as you add it. Fold a pleat into the middle of a large piece of baking paper and place over the pudding. Cover with a large piece of pleated foil, ensuring the pleats are on top of one another. Secure tightly with kitchen string tied under the lip of the pudding basin.
Place an upturned saucer into a large saucepan one-quarter full of water. Fold a long piece of foil into quarters lengthways to create a long strip and place the pudding basin in the middle of the strip. Bring the sides of the strip up the sides of the pudding basin and lower into the saucepan. Ensure the water in the saucepan comes one-third of the way up the side of the pudding basin, but nowhere near the top of the basin. Leave the ends of the foil strip hanging over the side to make it easy to remove the pudding later.
Bring the water to the boil and then reduce the heat to a gentle simmer. Simmer gently for 5-6 hours, topping up the water level as necessary throughout cooking (do not allow the pan to dry out).
Once the pudding is cooked, remove from the pan and set aside to cool. The pudding can be stored for up to two years in a cool, dry place. To serve, reheat the pudding by steaming again (in the same way) for two hours, or until hot all the way through. Alternatively, remove the foil and reheat in the microwave.