Tangzhong: in a small pot over medium heat, whisk together the flour and water. Whisk constantly to remove any lumps and continue whisking until you have a thick paste. Set aside to cool to room temperature.
Dough: in a stand-mixer with a dough hook, add in all your Dough ingredients & the cooled tangzhong. Let the stand-mixer go for 7-10 minutes or until everything combined and the flour should slightly pull away from the sides but will still be very sticky. You can, of course do this by hand - just knead for approx 15 minutes.
First Proof: transfer dough into an lightly oiled bowl, cover and let proof for 1.5 hours or until doubled in size.
Shaping & Second Proof: punch the dough to release gas and divide the dough into 15 even pieces. Roll them tightly into balls and place evenly into a well-buttered baking pan. Cover and let proof for another 1 hour or until doubled in size.
Bake: 30 minutes before the dough is done proofing, pre-heat your oven to 180C/ 350F. Brush over the dough balls with egg wash and bake for 25-30 minutes or until golden brown. Remove from oven and immediately brush on melted butter and sprinkle over sea salt.