01 - Combine warm milk, sugar, and 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. Stir until thoroughly incorporated.
03 - Gradually add flour, 1 cup at a time, mixing until a soft, tacky dough forms. You may not need all the flour depending on humidity.
04 - Knead dough on a lightly floured surface for 7–8 minutes until smooth, elastic, and passes the windowpane test.
05 - Place dough in a lightly greased bowl, cover with plastic wrap or damp towel, and let rise until doubled in size, approximately 1 to 1.5 hours.
06 - Punch down dough and divide into 8 equal pieces. Roll each piece into a smooth log about 6 inches long, tapering ends slightly.
07 - Arrange shaped buns on a parchment-lined baking sheet, spacing 2 inches apart. Cover and let rise until puffy, 30–45 minutes.
08 - Preheat oven to 375°F.
09 - Brush buns with milk and sprinkle with seeds if using. Bake for 18–20 minutes until deep golden brown.
10 - Remove from oven and immediately brush with melted butter for a softer crust. Cool completely on wire rack before slicing.