01 - In a large bowl, combine the flour, sugar, salt, mixed spice, and cinnamon. Position the yeast on one side of the bowl and salt on the opposite side to prevent yeast inhibition.
02 - Add the softened butter, lukewarm milk, and egg to the dry ingredients. Mix thoroughly until a soft, cohesive dough forms.
03 - Knead by hand on a lightly floured surface or with a stand mixer fitted with a dough hook for 10 minutes until the dough becomes smooth, elastic, and passes the windowpane test.
04 - Transfer the dough to a lightly oiled bowl, cover with plastic wrap or a damp cloth, and place in a warm, draft-free area. Let rise for 1 hour or until doubled in volume.
05 - Punch down the risen dough to release air. Knead in the currants, candied peel, and orange zest until evenly distributed throughout the dough.
06 - Divide the dough into 12 equal portions, approximately 85g each. Shape each piece into a smooth, tight ball and arrange on a parchment-lined baking sheet, spacing 2 inches apart to allow for expansion.
07 - Cover the tray loosely with a clean tea towel and let rise in a warm place for 45 minutes until the buns are visibly puffed and touching each other.
08 - Preheat the oven to 400°F with rack positioned in the center.
09 - Whisk the plain flour with 5-6 tablespoons water in a small bowl until a thick, pipeable paste forms. Adjust consistency with additional water if necessary.
10 - Transfer the paste to a piping bag fitted with a small round tip or a zip-top bag with a corner snipped. Pipe a continuous cross over the center of each bun.
11 - Bake for 20-25 minutes until deep golden brown and the bottoms sound hollow when tapped. Rotate the tray halfway through for even browning.
12 - While the buns are still hot, warm the apricot jam until fluid and brush generously over the tops using a pastry brush to create a shiny finish.
13 - Transfer the buns to a wire rack and cool completely. Serve warm, toasted with butter, or at room temperature.