In a glass measuring cup, combine the water, milk, yeast and sugar. Let stand until foamy, about 5 minutes. Meanwhile, beat 1 egg in a separate bowl; set aside.

In the bowl of a stand mixer, add the flours, salt and butter. Using the paddle attachment, mix the ingredients until the butter is the size of small crumbs.

Add the yeast mixture and beaten egg to the bowl. Run the mixer on medium-low (I used #3 on my Kitchen Aid) until a dough forms, about 8-10 minutes.

Shape the dough into a ball and return it to the bowl (it will be sticky). Cover with plastic wrap and let the dough rise in a warm place for about 1-2 hours. Transfer to the refrigerator to finish rising overnight.

When you are ready to bake, remove the dough from the refrigerator and bring to room temperature, about 1 hour.

Line a baking sheet with parchment paper.

Using a bench knife (or chef’s knife), divide the dough into 8 equal pieces. If you have a kitchen scale, weigh each piece to guarantee that they’re all the same size.

To shape the dough into balls, gently flatten each piece like a pancake. Pull up each side pinching it together in the center. Repeat until the ball is sealed. Flip the ball over (seam side down) and move to an un-floured part of your board (it’s easier to roll this way). Place your palm over the top and gently roll into a smooth ball.

Transfer the balls to a parchment lined baking sheet, placing them 2 to 3 inches apart. Gently press down to flatten. Cover loosely with lightly oiled plastic wrap and let buns rise in a warm place for 30 minutes to 1 hour, or until puffy and slightly risen.

To make the egg wash, beat the remaining egg with a splash of water. Right before baking, gently brush each bun with egg wash, making sure to coat the sides and underneath the dough. Sprinkle sesame seeds over the top.

Preheat your oven to 375 F. and place a shallow metal baking pan on the oven floor. Before the dough goes in, add a few ice cubes to the hot pan to create steam. This will keep the bread moist and prevent it from tearing on the sides.

Bake for about 20-25 minutes or until golden brown.

Transfer to a wire rack and cool completely before serving.