• Add the flour, water, sourdough starter, sugar and salt to the bowl of a stand mixer fitted with the dough hook attachment.
• Set the mixer to low speed and mix until fully combined and a shaggy dough forms. Cover and let rest for about 15 minutes.
• Set the mixer to low speed again and knead the dough for 5-7 minutes. Cover and let rest another 30 minutes.
• Once again, set the mixer to low speed and slowly add the soft butter to the mixture. Continue to mix until the dough is fully combined and no chunks of butter remain (about 5-7 minutes).

Bulk Fermentation

• Cover the bowl with plastic wrap. Allow the dough to rise at room temperature until it increases in size by about 75% (usually about 6-8 hours).

  Watch the dough rather than clock as the temperature of your home can greatly affect how long this takes.

Shape the Dough

• Line a loaf pan with parchment paper with the paper coming up the long side of the pan. The short edges of the pan should be free of paper.
• Transfer the dough to a lightly floured work surface.
• With floured hands, gently pull the edges of the dough so that it forms a rough square about the width of your loaf pan.
• Roll the dough into a cylinder and slightly tuck the edges underneath the dough.
• Carefully transfer the dough to the loaf pan, seam side down.

The Second Rise

• Loosely cover the loaf pan with plastic wrap.
• Allow the dough to rise a second time until the dough doubles in size and appears smooth on top. It should be peaking over the top of the loaf pan when fully proofed.

Bake

• When the dough is ready to bake, preheat the oven to 350℉.
• Remove the plastic wrap and bake in preheated oven for 50 minutes. The top should appear lightly golden brown when done.
• Allow to cool in pan for a few hours. Then, remove from pan and allow to cool completely on a wire rack at room temperature before transferring to storage bag.