Preheat your oven to 300°F (150°C). Line a 9-inch round cake tin with parchment paper, ensuring it extends beyond the edges for easy removal.
In a large saucepan, combine the milk, golden syrup, butter, dates, golden raisins, raisins, currants, and candied peel. Gently heat the mixture, stirring occasionally, until the butter melts and the ingredients are well combined. Let it cool to room temperature.
In a separate bowl, sift together the flour, pumpkin pie spice, and baking soda. Stir in the chopped walnuts to coat them in the flour.
Once the fruit mixture is cool, beat in the eggs one at a time. Gradually fold in the dry ingredients, mixing until just combined. Avoid overmixing to keep the cake light.
Spoon the batter into the lined cake tin, ensuring an even surface. Bake for 2 to 2½ hours, checking doneness with a skewer—it should come out clean when ready. If the top starts to darken too much, loosely cover it with foil to prevent over-browning.
While the cake is still warm, poke holes across the top with a skewer and drizzle over 2 tablespoons of brandy (or your chosen spirit). Allow the cake to cool completely in the tin.
Remove the cake from the tin and wrap it tightly in parchment paper and foil. Over the next few weeks, “feed” the cake with the remaining brandy every few days to deepen the flavor. Store in a cool, dark place.