- In a bowl, beat 1 egg with a whisk. Add ¾ cup (180 ml) of the water, the milk, sugar and yeast.
- In a stand mixer fitted with the dough hook, combine the flour, butter and salt into a rough dough. Add the egg mixture. Knead on medium speed for 5 minutes or until smooth. Using your hands, form the dough into a ball and place in a clean, lightly oiled bowl. Cover with plastic wrap. Let rise in a warm, humid spot for 1 hour 30 minutes or until doubled in volume.
- Line a baking sheet with a silicone mat or parchment paper.
- Turn the dough out onto a lightly floured work surface. Cut the dough into 8 equal pieces. Roll each piece of dough against the work surface into a ball using the palm of your hand. Transfer to the prepared baking sheet, leaving space between each ball. Cover with plastic wrap and let rise for 1 hour or until doubled in volume.
- With the rack in the middle position, preheat the oven to 375°F (190°C).
- In a small bowl, using a fork, combine the remaining egg with the remaining water. Using a pastry brush, cover the top of each ball of dough with the egg wash. Sprinkle with sesame seeds, if desired.
- Bake for 20 minutes or until the buns are nicely golden. Let cool. The buns will keep for 2 or 3 days in an airtight container at room temperature.