Mill 2–2½ cups hard white wheat berries to make 3–3½ cups freshly milled flour. Set aside.
Preheat oven to 425°F (220°C). Line a baking sheet with parchment paper.
In a large bowl, combine 1 cup + 2 tablespoons warm water (110°F), 2 tablespoons instant yeast (or active dry), ¼ cup sugar, and ⅓ cup olive oil. Stir and let sit 5–10 minutes, until foamy.
Whisk in 1 beaten egg and 1 teaspoon salt.
Transfer mixture to a mixer. Gradually add freshly milled flour, mixing until a soft, slightly sticky dough forms (up to 3½ cups flour). Scrape sides as needed.
Knead with the mixer for about 5 minutes, until smooth and elastic.
Punch down dough and divide into 8 equal pieces.
Shape into smooth balls and place on prepared baking sheet.
Cover loosely and let rise 10–15 minutes, until puffy.
Whisk 1 egg yolk with 1 tablespoon water. Brush over buns and sprinkle with 2 tablespoons sesame seeds.
Bake at 425°F (220°C) for 12 minutes, until golden brown.
Cool on a wire rack for at least 10 minutes before slicing.