01 - Combine the warm milk, sugar, and yeast in a large mixing bowl. Let the mixture sit for 3–5 minutes until it becomes bubbly and foamy, indicating the yeast is active.
02 - Add the sourdough discard, melted butter, egg, and salt to the activated yeast mixture. Whisk until all ingredients are thoroughly incorporated.
03 - Gradually add flour, 1 cup at a time, mixing after each addition. Continue adding flour until a soft, tacky dough forms. You may not need all the flour—the dough should be pliable but not sticky.
04 - Turn the dough onto a lightly floured surface. Knead for 7–8 minutes, pushing the dough away with the heel of your hand and folding it back over itself, until smooth and elastic.
05 - Place the dough in a lightly greased bowl, turning once to coat all sides. Cover with plastic wrap or a clean towel and let rise in a warm, draft-free area until doubled in size, approximately 1–1.5 hours.
06 - Punch down the risen dough to release air bubbles. Divide into 8 equal pieces and shape each into a smooth log about 6 inches long, tapering the ends slightly.
07 - Arrange the shaped buns on a parchment-lined baking sheet, spacing them 2 inches apart to allow for expansion. Cover and let rise until puffy and noticeably increased in size, 30–45 minutes.
08 - Preheat the oven to 375°F (190°C) during the final 15 minutes of the second rise to ensure it reaches the proper temperature.
09 - Brush the buns with milk and sprinkle with seeds if using. Bake for 18–20 minutes until the tops are golden brown and the buns sound hollow when tapped on the bottom.
10 - Remove from the oven and immediately brush with melted butter for a softer, more flavorful crust. Transfer to a wire rack and cool completely before slicing to prevent crumbling.