01 - In a large bowl, combine the bread flour, caster sugar, mixed spice, cinnamon, salt, and lemon zest. Add the instant yeast to one side of the bowl and keep the salt on the opposite side.
02 - Create a well in the center of the flour mixture. Add the softened butter, lukewarm milk, and beaten egg. Mix thoroughly to form a sticky, cohesive dough.
03 - Turn the dough onto a lightly floured surface and knead for 10 minutes until smooth, elastic, and no longer sticky. The dough should spring back when pressed lightly.
04 - Place the dough in a lightly oiled bowl, cover with plastic wrap or a damp towel, and let rise in a warm, draft-free area for 1 hour or until doubled in size.
05 - Punch down the risen dough and knead in the currants, sultanas, and mixed peel until evenly distributed throughout the dough.
06 - Divide the dough into 12 equal portions. Shape each piece into a smooth, tight ball by tucking the edges underneath.
07 - Arrange the buns on a parchment-lined baking tray, leaving slight space between them. Cover and let rise for 45 minutes until noticeably puffed and touching.
08 - Mix the plain flour and water to form a thick, pipeable paste. Transfer to a piping bag or zip-top bag with the corner snipped.
09 - Pipe a cross over each risen bun using the flour paste, ensuring lines are even and centered.
10 - Bake at 400°F for 20-25 minutes until golden brown and hollow-sounding when tapped on the bottom.
11 - Warm the apricot jam in a small saucepan until fluid. Brush generously over the hot buns immediately after removing from the oven for a glossy finish.
12 - Transfer the buns to a wire rack to cool completely. Serve warm with butter for optimal flavor and texture.