Put the warm water and milk together in a small bowl and sprinkle over the yeast. Leave a couple minutes to start to activate while you prepare other ingredients. Note the water & milk mix should just be tepid, not hot, so it doesn't kill the yeast.
Set aside 2 tablespoon of the butter for later. Whisk together the remaining melted butter, sugar and egg yolks until well combined.
Add the yeast mixture to the butter-egg mixture and mix then add the flour and salt. Mix well so it comes together as a ball of dough. The dough should be pretty soft and slightly sticky but still come away from your hands and the bowl easily. If too soft, add a little more flour, and if it feels dry, add a little more milk.
Knead the dough slightly for a couple minutes then put in a bowl, cover with a cloth or cling wrap/film and set aside in a warm room-temp for approx 40 mins - 1 hour until the dough doubles in size.
Prepare a baking sheet/tray by lining with a silicone mat or parchment. (A light colored baking sheet is recommended so the base doesn't darken too much.)
Gently knock back (deflate) the dough and divide into 6 equal pieces. Roll each piece on a lightly floured surface into a smooth ball then roll it out into a long rope, around ¾ inch (2cm) thick and 18 inches (45cm) long. Roll up the rope of dough in a coil so it's touching the dough next to it but not overly tight. Brush the side of the dough with a little melted butter as you go to help it stick. Transfer to the prepared baking sheet.
Repeat with the remaining pieces of dough and make sure you leave a good 2 inches (5cm) or more between the dough coils. Lightly cover the tray and leave at warm room temp for around 40 mins - 1 hour to double in size again - it can be hard to tell but you should see a noticeable increase in size.
Pre-heat the oven to 375F/190C. Brush the top of the rolls with additional melted butter then bake for approx 12-15 minutes until the tops are golden. Allow to cool slightly then sprinkle with powdered sugar/icing sugar before serving.