Step 1

Combine the dry yeast with the water. Whisk in the sugar, flour, and salt. Let sit uncovered on the counter for 4-6 days. Whisk 4-5 times daily.

Step 2

Scald the milk in a small saucepan. Stir in the sugar to dissolve. Let cool to lukewarm. Pour the warm water into the bowl of a stand mixer or a large bowl; sprinkle with yeast and stir until dissolved. Add the milk mixture, sourdough starter, salt, and 3 cups of the flour. Mix with the dough hook until smooth. Cut the butter into pieces and incorporate. Add enough of the remaining flour to make a smooth dough.

Step 3

Turn dough out onto a floured surface and knead until smooth and elastic, 4-5 minutes. Form into a ball and place into a greased bowl, turning to coat all sides. Cover with plastic wrap and let rise in a warm place until doubled, 1 - 1/4 hours.

Step 4

Punch down dough and let rest for about 15 minutes. Grease two 9 x 5-inch loaf pans. Divide the dough in half and shape into loaves. Transfer the dough to the loaf pans and make a cut on the top of each loaf with a sharp knife or new razer blade. Spray some plastic wrap with cooking spray, so that it doesn't stick, and loosely cover the loaves. Let rise in a warm area until doubled, about 1 - 1 1/4 hours.

Step 5

Preheat the oven to 400 degrees F. Bake for about 40 minutes, or until golden brown. Let cool for 10 minutes. Remove from the bread pans and let cool completely.

Step 6

Note: Lodge brand cast iron bread pans are great for making bread! Place a pan of water on the rack below the bread in the oven. The steam created will make a crunchy crust.