• You need to make sure your sourdough starter is bubbly and ready to go. If it has not been fed recently, take a few spoonfuls of sourdough starter from your fridge and give it that much flour and water and let it ferment for 6 - 8 hours. Here is more help for a bubbly sourdough starter. How to care for your sourdough starter
  

Stuffing

• Dice the onion and celery into tiny pieces. Melt the butter in a pan over medium-high heat. Add the onions and celery to the pan with the poultry seasoning and sauté in the butter until tender but not browned (about 4 minutes).
  

Making the dough

• Add the bubbly sourdough starter and warm water to a large bowl. Mix them together with a whisk or a fork until well combined.
  
• Add the flours and salt and combine with a stiff spatula. You can also use your hands to get the flour fully incorporated into a shaggy dough. Then cover the bowl with plastic wrap or a damp cloth and let sit for 30 minutes.
  
• After 30 minutes, gently knead the vegetables into the dough and knead for about a minute. Add a little flour if the dough feels too sticky, but it should be a little moist. Place the dough back in the bowl and cover with plastic wrap. Let it rise overnight for 8-10 hours (around 70°F) or until the dough has risen in the bowl and looks puffier.
  

Making and Baking the Bread

• Using a dough scraper or spatula, gently pull the dough from the bowl onto a lightly floured work surface. Line a 10-inch proofing bowl with a towel and dust generously with flour.
  
• Place in the proofing basket seam side up. Cover the bowl and let it rest until puffy but not fully risen (about 30 to 60 minutes).
  
• In the meantime, preheat your oven to 450°F. Cut a piece of parchment paper to fit your pot leaving excess so you can grab the bread and take it out of the pot.
  
• Place your parchment paper over the bowl and invert the bowl to allow the bread to release onto the paper.
  
• With a small razor blade or serrated knife, score the bread with four slashes. Pick up the parchment and carefully place your bread in the pot.
  
• Put the lid on the pot and place it in the oven for 20 minutes. Then remove the lid and continue baking for 30 more minutes. You can test it with a thermometer, and it should read 205-210℉.
  
• When the bread is done, take it out of the pot and place it on a wire rack to cool for about 20 minutes to an hour.
  
• Store the loaf in a bag on the counter. This bread freezes beautifully.