In the bowl of a stand mixer, mix together all dry ingredients then add the water, butter and 2 tbsp. of the beaten egg reserving the rest for later.
Mix all ingredients with a spatula until a dough forms. If you find it too dry, mix in water by the teaspoon until a slightly sticky mass if formed. Then knead using a dough hook until a smooth dough has formed, about 10 minutes.
Form a ball with the dough and let rise in a warm area until doubled in size, about 1 hour to 1 hour and 30 minutes.
Deflate dough, split equally into four pieces and place on a baking sheet lined with parchment paper. Let the dough proof a second time for 30-45 minutes to let the dough settle and increase in size.
While the dough is proofing for the second time, heat oven to 375°F.
Just before baking, add 1 tbsp. of water to the remaining beaten egg and brush each bun lightly with the mixture. Then sprinkle with sesame seeds if you wish.
Bake until they are a deep golden colour, about 15 to 18 minutes.
