Using a countertop mixer, add flour, yeast, salt and sugar; stir until well combined.

In a separate bowl, whisk together milk, oil, egg and additional egg yolk until well combined. (Tip: Save extra egg white as it will be used later!)

Pour liquid mixture into bowl of countertop mixer. Using dough hook attachment, mix for 3-4 minutes on medium-high speed. (Note: The dough should pull away from the sides of the bowl. If it does not, add more flour 1 Tbsp at a time until it does. Likewise, if there is flour still at the bottom of the bowl, add more milk 1 Tbsp at a time until dough comes together.)

Transfer dough into a large oiled bowl. Cover with plastic wrap and place in a warm location until dough has doubled in size (~60-75 minutes).

Turn dough out onto floured countertop and fold several times. Divide dough into 10 equal pieces. (Note: A kitchen scale is a great way to ensure equal sizes.)

Shape each piece into a tight ball and then flatten each ball into a 3” disk. Place disks on parchment-lined baking sheet. Cover and place in a warm location to rise until almost doubled in size (~45-60 minutes).

Preheat oven to 375°F.

In a small bowl, combine onion flakes, garlic flakes, poppy seeds, sesame seeds and kosher salt. Stir until well combined.

Whisk together egg and water to create egg wash. Brush tops of buns lightly with egg wash and sprinkle with Everything Topping mixture.

Bake buns at 375° for 12-14 minutes, or until tops of buns turn light golden brown.

Remove buns from oven and immediately brush with melted butter. Let buns cool completely before slicing.