Place yeast into the bowl of a large stand mixer; whisk in 1/2 cup flour and warm water until smooth. Let stand until mixture is foamy, 10 to 15 minutes.

Whisk 1 egg, melted butter, sugar, and salt thoroughly into the yeast mixture. Add remaining flour (about 3 cups).

Fit a dough hook onto the stand mixer and knead dough on low speed until soft and sticky, about 5 to 6 minutes. Scrape sides if needed.

Transfer dough onto a floured work surface and gently form into a smooth, round shape.

Wipe out the stand mixer bowl and drizzle with olive oil. Add dough, turning to coat. Cover and let dough rise in a warm place until doubled in size, about 2 hours.

Line a baking sheet with silicone mat or parchment paper.

Transfer dough to a floured work surface and form into a rectangle. Cut into 8 equal pieces, form each piece into rounds, and stretch into 1/2-inch discs.

Place discs on the baking sheet, dust lightly with flour, cover with plastic wrap, and let rise until doubled, about 1 hour.

Preheat oven to 375°F (190°C).

Beat remaining egg with milk. Brush tops of buns with egg wash and sprinkle with sesame seeds.