Pour the warmed milk into a bowl, add in the sugar and yeast.
Give it a stir and let the yeast activate and bubble.
In a bowl of a stand mixer fitted with a dough hook, add in the flour, about 75% of the egg (remember to save some for the eggwash later), oil and sea salt.
Start the mixer on low and pour in the activated yeast and milk. Add in the cooled tangzhong.
Knead until the dough starts to come together and forms a smooth and shiny ball, about 7-8 minutes of kneading.
Put the dough into a lightly greased bowl and cover with plastic wrap. Place in a warm location and let the dough double in size (approximately 60-90 mins, depending on how warm your kitchen is).
Prepare a baking sheet with parchment paper. Set aside.
Once the dough has risen, deflate the dough and divide into equal portions, about 62g each.
Divide the pork filling into 8 equal portions, about 55g each and place onto a plate.
Tip: Use a large ice cream scooper to portion out the filling, and that way you can transfer the filling onto the bun easily.
Roll out each portion of dough into a round disc, with the outer edges slightly thinner than the centre.
Place the BBQ pork filling in the centre of the dough, being careful not to get any sauce near the edges. Any sauce or moisture will prevent the dough from sealing properly.
Carefully gather the edges of the dough and pleat to seal the bun.
Place the bun seam-side down onto a piece of parchment paper.
Repeat with the remaining buns.
Cover the buns loosely with plastic wrap and leave to rest for about 30 minutes in a warm location, or until fully proofed.