Combine all of the dough ingredients, except the semolina, in the bowl of a stand mixer fitted with the dough hook.

Mix to form a smooth dough, but watch your electric mixer carefully; it was a tough load on mine. The dough should be soft and elastic, but not particularly sticky; add additional flour if necessary.

Remove the dough to a lightly greased bowl, cover, and set it aside to rise for about 1 1/2 hours, or until it's noticeably puffy. (I use my enameled cast iron for this; the lid is a perfect cover and it conducts heat well, so if you rise in a warm oven, it works even better.)

For most pronounced sour flavor, cover the bowl, and immediately place it in the refrigerator (without rising first), allowing the dough to chill for 24 hours; this will develop a more intense sour flavor.

After the dough has risen, gently deflate it, turn it out onto a lightly floured work surface, and cover it, letting it sit for a few minutes to relax the gluten.

Using a sharp knife, divide the dough in half.

Working with one piece at a time, roll it out to 1/2" thickness and cut in 3" rounds. (If you don't have biscuit cutters, you can use a drinking glass dipped in flour.) Re-roll and cut any remaining scraps. Repeat with the remaining half of dough.

Line a rimmed baking sheet with semolina and evenly place the rounds on it (12 per sheet). Sprinkle them with additional semolina, cover with plastic wrap, and let them rise until light and puffy, about 45 to 60 minutes. If the dough has been refrigerated overnight, the rise time will be about 2 hours.

Heat an ungreased skillet (cast iron works great for this!) on the stove over medium heat and carefully transfer the rounds (as many as will fit without crowding) right-side up (small rounds allowed for 5 to cook at a time; larger ones limited me to 4).

Cook the muffins for about 5-7 minutes on each side. The edges may feel a bit soft, but that's OK. Be sure to flatten with a pancake turner after each side has cooked for 1-2 minutes, to keep them from puffing up too much.

Remove to a wire rack to cool completely. Store tightly wrapped at room temperature for 4 or 5 days; freeze for longer storage.