Weigh the water and yeast into the bowl of a stand mixer and mix together.
Add the remaining ingredients, starting with the wetter ingredients, then the dries, ending with the butter.
Using your hand, mix everything together till just incorporated, then scrape your hand clean and knead the dough with a hook attachment in the mixer. Start with 5 minutes on speed 1, then increase to speed 2 and mix until the dough looks smooth and you get a window pane when you stretch a piece of dough between your fingers - this will take around 15 minutes, possibly up to 20. You will need to scrape the bowl down a couple times during mixing, as the dough will be very sticky.
Place the dough in a greased bowl and cover with a damp tea towel. Let the dough rise until almost doubled, about 1 hour.
Deflate the dough and portion it into 15x 50g pieces. Round the portions into tight balls. Place all 15 onto a lined and lightly greased quarter sheet tray for their final proof - about 1 1/2 to 2 hours.
Towards the end of the final proof (the buns will be very puffy and touching each other), preheat the oven to 190℃/375℉. Brush the rolls carefully with egg wash.
Place the rolls in the oven and immediately lower it to 180℃/350℉. Bake for about 20-25 mins. You're aiming for an internal temp of 190-200 F and buns with a lovely golden brown colour!
