1. For tangzhong: Add flour and milk to a small pot. Heat over medium heat while stirring with a whisk until the mixture thickens, and the temperature has reached 65ºC.
2. Transfer to a bowl and cover with plastic wrap (to avoid a skin forming, make sure the plastic wrap touches the entire surface of the dough). Cool to room temperature.
3. For babka: Add milk, yeast, sugar and tangzhong to a bowl, and mix with a stand mixer until combined.
4. Add eggs and mix for a further 2 minutes, then add sifted flour and continue mixing for approx. 5 minutes until combined.
5. Let rest for 5 minutes before adding salt. Knead at medium speed for 5 minutes.
6. Slowly add in the cubed butter one cube at a time. When all the butter is added, scrape down sides of mixing bowl and continue mixing at medium speed for roughly 15–20 minutes. Transfer dough to a clean, lightly oiled bowl and proof in fridge overnight.
7. On a liberally floured surface, turn out the dough and form into a rectangle. Divide dough into 8 equal pieces.
8. With first piece of dough, roll out into a 16cm wide x 21cm long rectangle. Spread a few teaspoons of the filling evenly onto the rectangle and stop about ½ cm before the edge.
9. Roll rectangle tightly, horizontally, to form a log. Transfer log to a baking sheet, and repeat above steps with remaining pieces of dough.
10. Transfer baking sheet of logs to the freezer for approx. 5 minutes – this will help when cutting and forming them.
11. Spray a muffin tin with cooking spray and set aside. Remove baking sheet from freezer and trim a teeny bit off the edges on both sides of your rolls. For each log, cut in half lengthwise so the striations of the dough and filling are visible.
12. With cut sides facing up, place left side of log over the right and repeat with right over left until the two are halves are braided or twisted together.
13. Shape the braided dough into a circle, making sure the ‘ends’ go past the circle and overlap. Tuck the long end under and up through the centre hole, then trim off excess dough.
14. Repeat for each log, transferring all to the centre of a muffin tin when done. Cover tin with a clean kitchen towel and allow to rise for approx. 1 hour, until the rolls have clearly risen out of the tin.
15. Pre-heat over to 180ºC. Gently brush the tops of each bun with egg wash and transfer to oven to bake for approx. 15–20 minutes, until lightly golden brown.
16. Allow to cool in muffin tin for 5 minutes, then carefully move to a cooling rack before serving, using a small offset spatula if needed to release babkas from tin.