01 - Combine warm milk, sugar, and instant yeast in a large mixing bowl. Let sit for 3–5 minutes until mixture becomes bubbly and foamy.
02 - Add sourdough discard, melted butter, egg, and salt to the yeast mixture. Whisk until fully incorporated.
03 - Gradually add flour, one cup at a time, mixing with a wooden spoon or dough hook after each addition. Continue until a soft, slightly tacky dough forms. You may not need the full 4 cups of flour.
04 - Turn dough onto a lightly floured surface. Knead for 7–8 minutes, pushing dough away with the heel of your hand and folding it back over itself, until smooth and elastic.
05 - Place dough in a lightly greased bowl, turning once to coat all sides. Cover with plastic wrap or a clean towel. Let rise in a warm, draft-free area until doubled in size, approximately 1 to 1.5 hours.
06 - Punch down dough to release air. Divide into 8 equal portions. Roll each piece into a smooth log about 6 inches long, tapering the ends slightly.
07 - Place shaped buns on a parchment-lined baking sheet, spacing 2 inches apart. Cover loosely and let rise until puffy and doubled, about 30–45 minutes.
08 - Preheat oven to 375°F during the final 15 minutes of the second rise.
09 - Brush risen buns with milk and sprinkle with seeds if using. Bake for 18–20 minutes until golden brown on top and sounds hollow when tapped.
10 - Remove from oven and immediately brush with melted butter for a softer crust. Transfer to a wire rack and cool completely before slicing.