• Add the flour, water, sourdough starter, salt, and butter to the bowl of a stand mixer. Use the dough hook attachment to mix on low speed until a shaggy dough forms.
• Cover and let rest for 30 minutes.
• Knead the dough for 10-12 minutes. You can do this in your stand mixer on low speed or by hand. The dough should become less sticky and form a smooth ball.
• Cover and let rest for 6-8 hours or until increased in size by about 75%.
• Divide the dough into 12 equally sized pieces (about 90g each). For larger hamburger buns, divide into 6 pieces.
• Form into a smooth ball by pinching the edges toward the top. Place seam side down on a baking sheet lined with parchment paper. Allow to rest for another 2 hours.

When Ready to Bake

• Preheat oven to 400℉.
• Bring the water to a boil, then add the baking soda. Stir until fully dissolved.
• Off the heat, use a slotted spoon to submerge the dough balls, one or two at a time, for 45 seconds on each side. Return to baking sheet lined with parchment paper and lightly sprayed with cooking spray to prevent sticking.
• Score an X on the top of each bun using a lame, razor blade or sharp kitchen knife. Sprinkle with flaky sea salt or pretzel salt.
• Bake for 20-22 minutes for small rolls or 25-30 minutes for large rolls. The buns should appear a deep golden brown color.
• Allow to cool before cutting the rolls if using as hamburger buns.