Heat the milk in a small saucepan until it reaches 105 degrees, sprinkle yeast over the top, stir, and let rest until foamy, about five minutes.
Meanwhile, whisk together the melted butter and egg in a small bowl. Slowly pour into warm milk mixture, whisking to combine all wet ingredients.
In the bowl of stand mixer, add the flour, salt, and sugar. Using the dough hook, stir dry ingredients on low speed until combined. Slowly pour in wet ingredients and mix until the dough begins to come together, increasing speed to medium.
When dough begins to pull away from sides, increase speed to medium-high and knead with dough hook for 5 to 7 minutes, until dough is smooth and elastic.
Transfer to oiled bowl and cover with clean kitchen towel before placing in warm spot to rise for 45 minutes to 1 hour, or until doubled in size.
When dough has risen, preheat oven to 350 degrees. Cut dough into 104g rounds and roll into tight balls (it’s helpful to make your hands into the shape of Cs and roll towards the edge of the counter to create a good bun shape). Place on parchment paper lined baking sheet sprayed with baking spray and press down with palms to flatten slightly.
Cover once more with a clean dish towel and allow to rise for another 30 minutes.
Gently brush the tops of the buns with egg wash (1 egg + 1tablespoon water) and sprinkle with sesame seeds. Bake in preheated oven for 20 – 22 minutes, until buns are golden and sound hollow when thumped.
Remove from oven and allow to cool on wire rack.