In large mixing bowl or bowl of a stand mixer, combine water, yeast and sugar. Let it rest for 5 minutes until foamy.
Add the milk and the butter to a small microwavable jug and heat until the butter has melted.
Add flour, salt and milk/melted butter to the yeast mixture and using either a wooden spoon or the dough hook attachment on your stand mixer, mix on low speed until a dough forms.
Continue to knead by hand for 7 minutes or with the stand mixer for 5 minutes on medium speed until the dough is soft and springs back when lightly touched.
Shape the dough into ball and place in a large lightly greased bowl (or leave in the bowl of your stand mixer). Cover with a clean tea towel and let rise in a warm place for 1 hour or until doubled in size.
Lightly punch down the dough and turn out onto a clean work surface. Divide the dough into 8 pieces and roll into smooth balls. Arrange them on 2 baking trays lined with baking paper or a silicone liner, leaving plenty of room between each bun and leave to rise in a warm, draught free place for about 45 minutes or until almost doubled in size again and puffy.
Whisk egg wash ingredients together and lightly brush over the buns and sprinkle with sesame seeds. Bake at 200°C for 14 minutes until golden brown on top and underneath.