01 - In a large mixing bowl, combine the warm milk, sugar, and yeast. Let sit for 3–5 minutes until bubbly.
02 - Add the sourdough discard, melted butter, egg, and salt. Mix to combine.
03 - Gradually add flour, 1 cup at a time, mixing until a soft, tacky dough forms. You may not need all the flour.
04 - Knead the dough on a lightly floured surface for 7–8 minutes until smooth and elastic.
05 - Place the dough in a lightly greased bowl, cover, and let rise until doubled in size (about 1–1.5 hours).
06 - Punch down the dough and divide into 8 equal pieces. Shape each piece into a smooth log, about 6 inches long.
07 - Place shaped buns on a parchment-lined baking sheet, spaced 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 desired. Bake for 18–20 minutes until golden brown.
10 - Remove from oven, brush with melted butter for a softer crust, and cool completely before slicing.