In a large bowl or the bowl of a stand mixer, combine the dry ingredients: flour, yeast, sugar, spices and salt. Add the yeast and salt to opposite sides of the bowl so they don't come into direct contact.
Add the cooled tangzhong and melted butter, along with the warm milk, egg, orange zest, and dried fruit.
If using a stand mixer, fit with the dough hook and mix on speed 2 for 5 minutes. Increase to speed 4 and continue mixing until the dough is smooth, elastic, and has cleared the sides of the bowl (about another 3–5 minutes). Kneading times may vary depending on your mixer, so it's best to go by visual cues.If some fruit has collected at the bottom of the bowl, transfer the dough to an unfloured work surface and briefly knead by hand just until evenly incorporated. If kneading by hand, mix the ingredients until they come together into a shaggy dough. Transfer to a lightly floured surface, and knead until smooth and elastic (about 10-15 minutes). The dough will be very sticky at first but will become easier to work with the more you knead. Use a bench scraper if needed, and refrain from adding excess flour as this can make the buns dense.
Transfer the dough to a lightly oiled bowl and cover with cling film or a draped towel. Let the dough rise in a warm place for 1-1.5 hours or until doubled in size.
Lightly grease a 23 x 33 cm (9 x 13 in) baking pan. Punch down the dough and transfer to an unfloured surface. Using a knife or a bench scraper, portion the dough into 12 pieces. Use a scale if you want to be precise (mine are 85g each).
To shape each bun, pull the outer edges down and underneath, pinching them together to seal the bottom (If unsure, refer to the step-by-step photos). Place the bun seam-side down on the countertop and roll it in a circular motion to create tension — this smooths the bottom and forms a tight, round ball. Place the buns in the prepared pan, spacing them about 1 to 2 cm apart. NOTE: As you shape the buns, keep the rest of the dough pieces covered to prevent them from drying out. Cover the baking pan and let the buns rise for 40–50 minutes, until they are puffy and starting to touch. In the meantime, preheat the oven to 180°C (160°C fan/350°F).