Combine the sugar, warm water, yeast, sourdough starter, flour, dry milk, butter, salt, and sour salt in a large bowl.
Mix and knead to form a smooth dough.
Place the dough in a lightly greased bowl, cover, and let it rise.
For a pronounced sour flavor, refrigerate the dough for 24 hours.
Deflate the dough and divide it into 24 pieces, shaping each into a round ball.
Flatten each ball into a 3" round and place on cornmeal-sprinkled baking sheets.
Cover and let rise until light and puffy, about 45 to 60 minutes.
Cook the muffins on a preheated griddle or frying pan for about 10 to 12 minutes on each side.
Remove from the griddle and cool on a rack.
