In the bowl of your stand mixer, combine 180g warm milk (~80f) , 100g warm water, 25g granulated sugar, and 7g instant yeast. Mix on low speed until the sugar is dissolved. Then add 100g sourdough discard, 500g bread flour and 6g sea salt. Mix until a rough, shaggy dough forms.
Gradually add 30g softened butter and mix until dough is smooth and elastic. Transfer to a greased bowl, cover and rest until nearly doubled in size.
Shape The Buns:
Line a baking sheet with parchment paper and set aside.
Turn the dough out onto a lightly floured surface, and press into a large rectangle. Cut the dough into 10 pieces, approximately 90g each, with a bench scraper or serrated knife.
Tuck each of the dough pieces into a tight ball and set on prepared baking sheet. Cover with plastic wrap and rest for 20 minutes.
Working one ball at a time, roll it into a rectangle about 6″ wide. Roll each rectangle into a cylinder, pinching the seams shut
Return each shaped bun, seam side down, to the prepared baking sheet, leaving a small gap between the buns. Cover with plastic wrap and allow to rise until nearly doubled.
Bake The Buns:
Once the buns have doubled, preheat the oven to 350f. Brush each bun generously with milk.
Bake at 350f for 20-25 minutes, until the tops are golden brown. You can check the doneness with an instant read thermometer, the internal temperature should be 190f.
Brush the top of the buns with butter, then allow to cool on the baking sheet before separating them.
Notes
Expert Tips
Brushing the buns with milk prior to baking helps give them a deep, rich color while brushing them after baking with butter helps to soften the crust and ensure the best bun possible.
I bulk ferment and proof my bread dough at room temperature, but if you’re in a warm place (warmer than 70-72f), your rising times will need to be shortened.
Allow the buns to rise until big and puffy before baking, this helps to ensure big, puffy buns.
Leave a small amount of space between the buns on the baking tray - we want them to have room to expand during the proofing process, but also to touch each other during baking to help keep their shape.
I find that adding a small amount of yeast gives these buns a little extra resiliency and bounce-back after shaping. Enriched sourdoughs, those with ingredients like eggs, butter, or milk, tend to perform better with a touch of yeast alongside the starter, helping the dough rise more predictably and maintain structure.