1. For the dough buns: Cut 8 squares of baking paper at 15cm x 15cm. Set aside.
2. Melt butter and allow to cool to about body temperature.
3. Add dried yeast to milk.
4. Add dry ingredients to bowl of a stand mixer (dough hook attached).
5. Mix on low speed. Add milk mix over 30 seconds.
6. Add eggs one by one.
7. Pour in butter. Mix for about 4 minutes, until dough is silky smooth, soft and elastic.
8. Put dough in a clean bowl (at least twice the size of dough). Wrap well and allow to prove at room temperature for about 90 minutes, or until nearly doubled in size. At this point, refrigerate the dough for 1 hour (it will be much easier to work with).
9. Turn dough onto a clean bench. Cut into 40g portions and roll into balls. Any excess dough balls can be used to make steamed pork buns, or stored in an airtight container and frozen for a later use.
10. Turn out dough onto floured workbench. Use a rolling pin to evenly roll the dough to 1.5cm thickness.
11. Use an 80mm round cutter to punch out donuts. Place them on a baking tray lined with baking paper and wrap well. Allow to prove at room temperature for about 90 minutes, or until doubled in size.
12. For sweet ricotta: Whisk all ingredients together.
13. Push into a disposable piping bag. Tie off the end and cut the tip at about 5mm wide.
14. For yuzu curd: In a mixing bowl, whisk together eggs, yolks, sugar and juice.
15. Place mix into a small saucepan over medium heat.
16. Whisk constantly as mix thickens, taking care not to let any curd caramelise or stick to the bottom of the pot. Once thick, remove and allow to cool slightly.
17. Off the heat, whisk in cubed butter pieces, one by one. Whisk well, ensuring to emulsify butter with curd.
18. Chill curd until ready to serve
19. Set up a 5L pot for deep-frying. Bring 1L of canola oil to 165°C.
20. Mix cinnamon and sugar in a bowl large enough to toss 2–3 donuts in.
21. Using a slotted spoon, place 2–3 donuts at a time in the fryer oil. Flip them over after 30 seconds, and again after 90 seconds. Flip donuts again as needed (they should be a deep golden brown colour). Drain donuts on a wire rack and use a skewer to check for doneness.
22. Repeat with remaining donuts.
23. Coat donuts very well in cinnamon sugar.
24. Use a small knife to poke holes in the bottom of each donut.
25. Pipe ricotta mix in, until the donut won’t hold any more.
26. Arrange on a plate and spoon over curd.