01 - Combine bread flour, caster sugar, mixed spice, cinnamon, nutmeg, and yeast in a large bowl. Position salt and yeast on opposite sides of the bowl to prevent yeast inhibition.
02 - Pour in softened butter, lukewarm milk, and beaten egg. Stir thoroughly until a soft, slightly sticky dough forms.
03 - Turn dough onto a lightly floured surface and knead vigorously for 8–10 minutes until smooth, elastic, and no longer tacky.
04 - Place dough in a lightly greased bowl, cover with plastic wrap or a clean towel, and let rise in a warm, draft-free area for approximately 1 hour until doubled in volume.
05 - Punch down risen dough to release air. Knead in currants, mixed peel, and orange zest until fruit is evenly distributed throughout the dough.
06 - Divide dough into 12 equal portions. Roll each piece into a smooth ball and arrange on a parchment-lined baking sheet, leaving slight space between buns.
07 - Cover loosely with oiled plastic wrap. Allow to proof for 45–60 minutes until buns are puffed and just touching each other.
08 - Heat oven to 400°F.
09 - Whisk plain flour and water in a small bowl until a thick, smooth paste forms. Transfer mixture to a piping bag fitted with a small round tip.
10 - Pipe a straight vertical line down the center of each bun, followed by a horizontal line to form a cross shape.
11 - Bake for 20–25 minutes until golden brown and buns sound hollow when tapped on the bottom.
12 - Warm apricot jam gently in a small saucepan or microwave until fluid. Brush generously over hot buns for a glossy finish.
13 - Transfer buns to a wire rack to cool completely. Serve fresh or toast before serving with butter.