In a medium sized bowl, add the water, milk powder, yeast and sugar. Whisk to combine.

In a separate bowl, beat the egg.

In the bowl of your stand mixer, add the bread flour, all-purpose flour, salt, and butter.

Turn on the mixer at the lowest speed, and mix until the butter is cut into the flour roughly the size of small pebbles.

Turn the speed up one notch. Stream in the yeast mixture and egg and knead, until a sticky dough forms, about 8 minutes.

Scrape down the sides of the bowl, and transfer the dough to a well-oiled surface. Shape the dough into a tight ball. The dough may be sticky.

Cover and let rest, until doubled in size, about 45 minutes.

When the dough has doubled, punch down to let the air out, and transfer to a lightly floured surface. Divide the dough into 8 equal-sized pieces. Divide into 6 for larger, oval-shaped buns.

Shape the dough into round buns. Flatten a piece of dough, then fold the edges to the center. Flip the dough over and roll into a ball.

Arrange the buns in a large baking sheet lined with parchment paper, leaving enough space in between.

Cover and let rest, until doubled in size, 45 minutes.

Preheat the oven to 200 degrees C (fan 180 degrees C). Place an empty metal baking pan at the bottom of your oven.

Make the egg wash. In a small bowl, add the egg and water, and beat until thoroughly combined.

Gently brush the risen buns with the egg wash, and sprinkle with sesame seeds, if using.

Right before putting the buns in the oven, pour ½ cup of water into the preheated empty tray to create steam. Bake until golden brown, 20 to 25 minutes.

Transfer to a wire rack and let cool.

Use as desired.