01 - Combine warm milk, sugar, and instant 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 sourdough discard, melted butter, egg, and salt to the yeast mixture. Stir thoroughly until all ingredients are fully incorporated.
03 - Gradually add flour, one cup at a time, mixing after each addition. Continue adding flour until a soft, tacky dough forms. You may not need the full 4 cups—stop when the dough holds together but still feels slightly sticky.
04 - Turn the dough onto a lightly floured surface and knead for 7–8 minutes. The dough should become smooth, elastic, and spring back when pressed with a finger.
05 - Place the dough in a lightly greased bowl, cover with plastic wrap or a clean towel, and let rise in a warm, draft-free area until doubled in size, approximately 1 to 1.5 hours.
06 - Punch down the risen dough to release air. Divide into 8 equal pieces and roll each into a smooth log about 6 inches long. Taper the ends slightly for a traditional hot dog bun shape.
07 - Arrange the shaped buns on a parchment-lined baking sheet, leaving about 2 inches of space between each. Cover and let rise until puffy and expanded, about 30–45 minutes.
08 - Preheat your oven to 375°F while the buns complete their second rise.
09 - Brush the risen buns with milk and sprinkle with seeds if using. Bake for 18–20 minutes until golden brown on top. The internal temperature should reach 190°F when fully baked.
10 - Remove buns from the oven and immediately brush with melted butter for a softer, more flavorful crust. Allow to cool completely on the baking sheet or a wire rack before slicing and serving.