Weigh the water and yeast into the bowl of a stand mixer and mix together.
Add the remaining ingredients, ending with the flours, sugar and salt.
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 15-20 minutes. You will need to scrape the bowl down a couple times during mixing, as the dough will be very sticky.
Place the dough into 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 14x 105g pieces. Round the portions into tight balls, then place onto lined and lightly greased trays. Press each ball down with your hand to flatten the bun - this will help it proof wider instead of taller. Then allow to proof for about 1-2 hours, depending on the temperature of your kitchen.
Towards the end of the final proof (the buns will be very puffy), preheat the oven to 375 F/ 190 C. Brush the rolls carefully with egg wash and sprinkle with sesame seeds.
Place the rolls in the oven and immediately lower it to 180℃/350℉. Bake for about 20-25 mins, rotating halfway. You're aiming for an internal temp of 190-200℉ and buns with a lovely golden brown colour!
