Prepare the fruit: In a large bowl, mix the raisins, currants, sultanas, and mixed peel. Pour over the brandy or rum and let the mixture soak for at least 24 hours, stirring occasionally.
Mix the dry ingredients: In a separate bowl, combine the suet, breadcrumbs, flour, sugar, almonds, citrus zest, and spices.
Combine the wet and dry: Add the grated apple, soaked fruit mixture, eggs, and milk to the dry ingredients. Stir everything together until well combined.
Prepare the pudding basin: Grease the pudding basin and spoon in the mixture, pressing it down firmly. Cover with a layer of greaseproof paper and foil, securing it with string.
Steam the pudding: Place the basin in a steamer or a large pot with simmering water (the water should reach halfway up the basin). Cover and steam for 4-6 hours, checking periodically to ensure the water doesn’t dry out.
Store the pudding: Once cooked, let the pudding cool. Store it in a cool, dark place for at least a week to allow the flavors to mature.
Reheat and serve: When ready to serve, steam the pudding again for 1 hour. For a show-stopping presentation, warm some brandy, pour it over the pudding, and light it with a match to flambé.