Combine ⅓ cup milk and ¼ cup bread flour in a small pan. Heat over medium-high heat and whisk until it comes together, about 1 minute. Set aside and allow to cool down.

Combine the yeast and milk and let it rest for 5 minutes, allowing the yeast to become active. Combine the bread flour, salt, and sugar in a large bowl of a stand mixer. Add the mixture in the pan, the yeast milk mixture, and egg. Mix until it just comes together.

Add 1 tablespoon of butter to the bowl. Mix until it is well incorporated, about 2 to 3 minutes. Continue adding the butter this way until all of it has been added. It is extremely important to do this very slowly. If you add the butter too quickly, the dough will never come together and will never gain the strength it needs to form.

Increase the speed to medium and knead the dough until it comes together into a ball, about 10 minutes. The dough is worked enough if it doesn’t rip when you tug it slightly. Transfer to a lightly floured work surface and shape into a rough ball.

Transfer to an oiled bowl, cover, and let rest for 1 hour or until it has doubled in size. Once doubled, punch down and knead. Prepare a baking sheet by placing parchment paper down.

Divide the dough into 12 equal portions (roughly 88 grams each). Shape into round balls and place on the baking sheet. Cover with a kitchen towel and let rest for 30 minutes, or until doubled in size.

Preheat an oven to 350°F. In a small bowl, whisk an egg and 2 tablespoons of milk. Remove the plastic wrap from the baking sheet and brush each of the buns with egg wash. Sprinkle generously with sesame seeds. Place in the oven and bake for 23 to 25 minutes or until golden brown.