Combine milk, yeast and caster sugar in a bowl. Stand for 10 minutes until foamy.

Meanwhile, sift flour, baking powder, salt and mixed spice into a bowl. Add yeast mixture, melted butter, egg and 3 teaspoons of the lemon rind; stir to form a soft dough.

Place dough in a large oiled bowl; cover with plastic wrap. Stand in a warm place for 1½ hours until dough almost doubles in size.

Grease a 23cm (9¼in) square cake pan. Line base and sides with baking paper (there is no need to extend the paper over the edge).

Turn dough out onto a 30cm x 50cm (12in x 20in) piece of baking paper. Place another piece of paper the same size on top. Roll dough out between baking paper into a 30cm x 40cm (12in x 16in) rectangle. Remove top paper.

Position dough with the long side in front of you. Spread dough with softened butter, leaving a 2cm (¾in) border on the opposite long side. Scatter with brown sugar and currants. Using the baking paper as an aid, roll up dough from longest side as tightly as possible into a log. Cut into 12 equal-sized pieces. Arrange slices, cut-side up in pan; cover with oiled plastic wrap. Stand in a warm place for 1 hour or until almost doubled in size.

Meanwhile, preheat oven to 200°C/400°F.

Bake buns for 25 minutes or until golden brown and they sound hollow when tapped. Transfer to a wire rack to cool.

Make glacé icing. Drizzle icing over buns; sprinkle with remaining 1 teaspoon lemon rind and the cinnamon.

Sift icing sugar into a small heatproof bowl; stir in enough of the lemon juice to make a thick paste. Place bowl over a small saucepan of simmering water; stir until icing is a pouring consistency (do not overheat).