Char siu bao using water roux

I made these char siu bao (bbq meat steamed buns) with a simple yeast dough. This is not the traditional smiling (cracked top) bao recipe which takes about 2 days to prepare. Traditional smiling bao also needs super white bleached fine milled flour (Hong Kong flour) which is not easy to find even from Chinese supermarkets in London. I used standard non bleached plain flour, the buns are not