Place raisins, sultanas, currants, nuts, and candied citrus peel in a bowl. Pour brandy over and stir thoroughly to coat every piece. Cover and let sit overnight to allow brandy to fully penetrate the fruit.

The next day, combine breadcrumbs, flour, baking powder, salt, brown sugar, mixed spice, and cinnamon in a large bowl. Stir well to distribute evenly.

In another bowl, add the soaked dried fruit mixture, grated apple, black treacle, suet, lemon and orange zest, and beaten eggs. Stir to combine thoroughly.

Add the dry mixture to the fruit mixture and stir until completely combined. The batter will be thick and sticky.

Generously butter your 2 liter (approximately 2 quart) pudding mold. Scoop batter into the mold, pressing down firmly to eliminate air pockets and smoothing the top.

Cut a circle of parchment paper the same diameter as the top of the pudding mold. Lightly butter one side and place butter-side down on top of the batter.

Cut two more pieces of parchment paper large enough to cover the top and partially down the sides. If batter comes to the top of the mold, fold a pleat in the center to allow for expansion. Secure with string, trimming excess paper.

Bring a large pot of water to a very low simmer. Place a folded cloth or trivet on the bottom of the pot to prevent direct contact with the pudding mold.

Lower the pudding mold onto the cloth. Water level should reach halfway up the mold. Cover pot with lid and steam over very low heat for a minimum of 6 hours but ideally 8 hours. Check periodically and add more hot water as needed to maintain level. The pudding will turn a beautiful dark brown - the longer it steams, the darker it becomes.

When done steaming, carefully lift out the pudding mold using tongs or thick oven mitts and let sit for 5 minutes. Invert onto a plate and let sit until pudding slides out. Cool completely.

To store, remove parchment paper and wrap pudding with clean parchment paper followed by aluminum foil. Wrap tightly and store in a cool, dark place like a basement for 4-6 weeks, or refrigerate for up to 6 weeks.

To serve, reheat by steaming for 30-60 minutes or microwaving in a covered microwave-safe container. For flaming presentation, warm 3-4 tablespoons brandy in a ladle, ignite carefully, and pour over pudding away from children. Serve with hard sauce, custard, whipped cream, or ice cream.