In a large mixing bowl, gently stir together yeast, warm milk, and sugar. Let sit for 10 minutes to bloom, then add melted butter, salt, and egg. Whisk together well, then add in about 3 ¼ cups flour.

Stir ingredients together well, then turn out onto a well-floured (using the other ½ cup of flour) work space to knead. Gently knead by hand for 5 minutes, or until dough is stretchy and only slightly sticky.

Separate the dough into 8-10 balls (depending on how big you want them) and place onto a baking sheet lined with parchment paper. Cover and let rise in a warm space for 15 minutes.

Preheat oven to 425 degrees F (218 C). Whisk the egg yolk and tablespoon of milk together and brush the egg wash over the tops and sides of the buns. Sprinkle with sesame seeds, if desired.

Bake for 10 to 12 minutes, until buns are golden brown.

These buns can be frozen for up to two months