Gather all your ingredients so that you have everything close at hand on the counter or table.
Prepare the Dough
In a large mixing bowl combine the active sourdough starter, warm water, softened butter, granulated sugar, instant yeast, kosher salt, dry milk powder, whole-wheat flour, and 2 cups all-purpose flour. Mix well.
Gradually add enough remaining all-purpose flour and knead to form a smooth dough, 5-7 minutes. Place dough in a greased bowl, cover, and let rise for 1-2 hours until noticeably puffy.
Preheat oven to 325 degrees. Gently deflate the dough, and turn out onto a lightly floured surface. Cover and allow to rest for 15 minutes to relax the gluten. Divide the dough in half.
Form and Cook the Muffins
Roll one of the halves 1/2" thick and cut in 4" rounds until all of dough is used. Repeat with the remaining dough.
Place the rounds, on baking sheets sprinkled with cornmeal, 8-9 per sheet. Sprinkle rounds with additional cornmeal. Cover and allow to rise 1 hour until light and puffy.
Transfer rounds to a preheated griddle (low heat). Cook the muffins for 5 minutes, and then place the bottom of a large cookie sheet on top to help flatten the muffins. Cook for an additional 5 minutes. Turn muffins and cook for another 5 minutes, being careful not to burn.
Place muffins on a baking sheet and allow them to finish cooking in the preheated oven for 5-10 minutes, while you cook the rest of the muffins.
Repeat with the remaining muffins. When finished, allow the muffins to cool on a wire rack.
Store in plastic bags for up to a week or freeze for longer storage. Makes 16-18 muffins.
Notes
*Unless otherwise indicated, all butter used on this recipe site is salted.