I made this polo bun quite often but there is a difficulty in handling the pastry as the butter melt very fast and cause it sticking on my hand while I'm trying to gather the dough with the pastry. Recently, I found another solution which would be much easier to handle. The original recipe asked to beat the butter until pale and fluffy then gradually add in sugar powder, salt and milk powder and beaten egg till everything combine. With this method you would get a wet pastry paste which you may need to store in the fridge for some time to harden before use (but it'll melt very fast in this hot weather, so it's not easy to handle).
For the new method, cut the cold butter into 1cm pieces (store them in the fridge if there start melting). With the same method as shortcrust pastry, process the flour, sugar powder, cold butter in a food processor till the butter mix thoroughly with the flour like the fine breadcrumbs. Add 1 tablespoon of beaten egg then pulse several times until its become a chunky breadcrumbs but not a dough (don't over process). Turn the pastry out onto a clean, floured work surface and, with floured hands, bring together to make a dough, but don't knead. Shape into a flattened ball, wrap in cling film and refrigerate for about 30 minutes. Divide the pastry into pieces and it's ready to use. I found that the texture is much better and most wonderful thing is, it's easily to put together the dough with the pastry.