For Water Roux : Mix milk with bread flour and stir well until it is no longer lumpy. Cook over medium low heat in a non-stick pot, stirringly constantly with a wooden spoon/rubber spatula/egg whisk, to prevent burning and sticking to the pot.

The tangzhong mixture is ready once it achieves the temp of 65 degrees celsius or once you see "lines" start to appear in the mixture every time you stir it. At this stage, the tangzhong should have the consistency and texture of glue.

Remove the pot from heat immediately and transfer the tangzhong into a clean bowl, and cover with clingwrap sticking onto the surface of the tangzhong to prevent it from drying up. The "tangzhong" can be used as soon as it cools down to room temperature. You can keep it chilled in the fridge for 2-3 days but discard it as soon as the mixture starts to turn grey.

For Dough : Prepare the tangzhong dough in advance. Allow the tangzhong to be cooled before using.

Mix milk, 1 tbs sugar and yeast in a mixing bowl, let it sit for 5 minutes to allow the yeast to begin to bubble and foam. Add in the egg, tangzhong, flour, remaining sugar and milk powder. With the dough hook, mix on low speed until the dough just comes together. Add in the salt and butter. Knead until the dough can be stretched into a thin stretchable membrane.

Put the dough in a greased bowl and cover it with greased clingwrap and proof in a warm place until doubled in size.

Fold it in half and press the seam to seal. Do the same thing for the remaining dough and filling.

Cover the pan with greased clingwrap and proof in a warm place until doubled in size.

Bake in a preheated oven 350°F for 40-45 minutes or until it's cooked. Sprinkle with permesan cheese 10 minutes before it's done (optional).