Soak the currants in the brandy for 10 minutes. Mix together the flour, cocoa powder, baking powder, baking soda, spices, salt, and dark chocolate. Mix well with a whisk.

Put the butter, sugar, vanilla, and lemon and orange zest in a stand mixer fitted with the beater attachment and beat to combine but not aerate much, about 1 minute. With the mixer running, slowly add the egg and mix for about1 minute. Add the dry ingredients, followed by the currants and brandy. Mix until everything comes together.

Gently knead the dough in the bowl with your hands until it comes together and is uniform. Divide the dough into 1¾-oz / 50g chunks and shape each chunk into a perfectly round ball. Place the balls on 1 or 2 baking sheets lined with parchment paper, spacing them about ¾ inch / 2 cm apart, and let rest in the fridge for at least 1 hour.

Preheat the oven to 375°F / 190°C. Bake the cookies for 15 to 20 minutes, until the top firms up but the center is still slightly soft. Remove from the oven. Once the cookies are out of the oven, allow to cool for only 5 minutes, and then transfer to a wire rack. While the cookies are still warm, whisk together the glaze ingredients until a thin and smooth icing forms. Pour 1 tablespoon of the glaze over each biscuit, leaving it to drip and coat the biscuit with a very thin, almost transparent film. Finish each with 3 pieces of candied peel placed at the center. Leave to set and serve, or store in an airtight container for a day or two.