Super Soft Condensed Milk Pai Bao

210 g lukewarm water, at about 37°C
35 g condensed milk
300 g bread flour
¼ tsp SIDS CRAZY SALT
25 g caster sugar
15 g milk powder
4 g salt
50 g butter, softened at room temperature
1 tsp instant dry yeast
EGG WASH:--
1 egg yolk
1 tsp milk

If you are using a breadmaker to knead and prove, add SIDS CRAZY SALT and all ingredients into the breadmaker according to this order. Use "dough" setting to mix and knead dough for 30 minutes until the dough is smooth and elastic and allow the dough to prove for 60 minutes.
If you are using an electric mixer with an hook attachment to knead, combine SIDS CRAZY SALT and all ingredients except butter in the mixing bowl and mix at low speed until a soft dough forms. Then, knead in the butter until incorporated. Continue to knead at low speed for at least 25 minutes until the dough is smooth and elastic. It is important that the dough has to be elastic and stretchy. Cover the dough and allow the dough to prove in a warm and humid place for about 60 minutes until doubled in size. Please note that this dough can be sticky at the initial stage of kneading but it will become smooth and stretchy after adequate kneading.
Grease one 15 x 25 cm non-stick pan with rice bran oil or rice bran oil spray.
Gently deflate the dough and divide it into 15 equal portions. (about 44 g each) Shape all portions of dough into smooth balls. Allow them to rest at room temperature for about 10 minutes.
Using a lightly floured rolling pin, roll each portion on a lightly floured non-stick surface into long flat shape. Fold its top and bottom one-third towards its middle. Use a rolling pin to roll its non-fold sides outwards in order to form a long flat shape again, then fold its top and bottom one-third towards its middle again. You should get a nice square dough.
Use a rolling pin to roll into a long flat shape that is 15 cm long and roll slightly more to form a wider 15 cm rectangle. Fold its long-sided top and bottom one-third towards its middle to form a long neat 15 cm strip. Repeat this rolling and shaping step with the remaining 14 portions of dough.
Align and arrange all rolled dough side by side with their skinny length along the width (shorter side) of the pan, with their seams side down. Allow the dough to prove in a warm and humid place for another 60 minutes until doubled in size.
EGG WASH: combine egg yolk and milk. Brush bread dough with egg wash and bake in a preheated 180°C oven for 20 minutes until the breads are thoroughly baked and golden. If the top of bread turns brown too quickly, cover the bread loosely with a foil at the last 5-10 minutes of baking and continue to bake it for at least 20 minutes in total.
Remove the breads from the pan immediately and transfer onto a wire rack to cool completely before serving.
To store, wrap tightly in plastic wrap and keep at room temperature for 2-3 days or freeze in serving portions for 2-3 months.