First, proof the yeast. Add Instant yeast to lukewarm water (Dry Active yeast needs water warmed to approximately 112ºF-like warm bath water). Add a pinch of sugar from the measured amount for the recipe to activate the yeast. Set the bowl aside and the mixture will start to get foamy.
Separate one of the eggs and set egg white aside.
Combine the yolk of 1 egg, whole eggs, and room temperature butter in the bowl of a stand mixer. Pour in yeast mixture and mix to combine.
In a separate bowl, combine potato flour, all purpose flour, sea salt flakes, and dry milk powder. Stir to make sure they are well combined.
Slowly spoon the dry ingredients into the wet ingredients with the mixer turned on.
Mix until all ingredients are well combined.
Either begin manual kneading or replace the mixing attachment with the dough hook attachment. For manual kneading fold one side of dough over the opposite side and punch down. Repeat this for approximately 15 minutes. Use all of the dough from the bowl. Scrape off the sides if necessary.
After kneading is complete, leave dough in the mixing bowl and cover the bowl with plastic wrap. Let dough rest (proof) for 1 hour.
After 1 hour, weigh the dough. Divide the dough into 6 equally weighted portions (for full size burger buns).
Roll the dough portions into balls and place on a parchment paper lined cookie sheet. Cover with plastic again for the 2nd proof. Dough portions will increase in size as they proof. Proof for another 45 minutes-1 hour. Dough is ready when it bounces back quickly after being poked.
As conclusion of the second proof approaches, whisk egg white with water to prepare egg wash and preheat the oven to 375°F.
Uncover dough portions, and use a pastry (silicone) brush to brush on the egg wash evenly.
Sprinkle sesame seeds over each egg-washed dough ball.
Bake for 15 minutes or until buns have a shiny, golden color and internal temperature reaches 190°F.
Remove from oven and cool before slicing.