100 mllukewarm milk, plus extra for brushing55 gm (¼ cup)raw caster sugar, plus extra for dusting pan17 gm sachet dry yeast3eggs, at room temperature450 gm (3 cups)plain flour50 gmvery soft butterFor dusting:demerara sugarMandarin jam8mandarins2each oranges and lemons220 gm (1 cup)white sugar60 ml (¼ cup)orange liqueurCinnamon glaze150 gmpure icing sugar, sieved30 mlmandarin juice10 gmbutter¼ tspground cinnamon
For mandarin jam, peel and segment half the mandarins. Remove seeds and reserve. Juice remaining mandarins into a measuring jug and set aside. Peel and segment oranges and lemons over a bowl to catch juices, then squeeze any remaining juice from pulp, reserving seeds. Combine juices to yield 1 cup and pour into a large heavy-based saucepan with sugar. Bring to a simmer over medium heat, stirring occasionally until sugar dissolves. Tie seeds in a small piece of muslin, add to pan with segments and simmer until syrupy (about 30 minutes). Remove seeds, stir in liqueur and cool to room temperature.
Meanwhile, combine milk, sugar and yeast in the bowl of an electric mixer fitted with a dough hook. Mix on low speed until yeast dissolves. Add eggs and ½ tsp sea salt and mix to combine. Add flour, mix to combine, then add butter and mix until incorporated. Increase mixer speed to medium and knead until dough is smooth and elastic (about 5 minutes). Transfer to a lightly oiled bowl, turn to coat, cover with plastic wrap and stand in a warm place until doubled in size (about 2 hours).
Preheat oven to 180C. Turn dough onto a floured surface, knock down, roll into a 20cm x 60cm rectangle. Working with the longest side facing you, spread with one-third of the jam, leaving a 3cm border. Roll to form a cylinder, cut into 12 even pieces and place cut-side down in a buttered and sugared 20cm x 30cm cake pan, allowing space for expansion. Cover with plastic wrap and stand in a warm place until doubled in size (30 minutes). Brush with milk, dust with sugar and bake until golden (30 minutes). Turn onto a wire rack and cool.
Meanwhile, for cinnamon glaze, combine ingredients in a small saucepan and stir over medium heat until smooth (about 2 minutes). Remove from heat, drizzle over buns and serve with jam passed separately.