In a large mixing bowl, add the proofed yeast mixture, 2 tablespoons of butter or oil, and 2 cups of sourdough discard.
Gradually stir in approximately 6 cups of flour and 1 teaspoon of salt with a wooden spoon until the dough starts to form. See Note.
Turn the dough onto a floured surface and knead for about 10 minutes until it’s smooth and elastic. Add more flour as needed if the dough is too sticky.
Place the dough back in a greased bowl, cover it, and let it rise in a warm spot until doubled in size, about 1 to 1.5 hours.
Punch down the dough. Using a scale and a bench knife divide the dough into two portions. Shape the dough it into loaves. Place in greased cast iron or stone loaf pans, cover with elastic bowl covers, and let rise again until doubled about 30-45 minutes. SEE NOTE
Preheat your oven to 400°F. Bake for 30-35 minutes until golden brown. Take the temperature of the loaf with a thermometer , the internal temperature in the middle of the loaf should be 200 degrees.
Let cool on a wire rack before slicing.