In a small bowl, mix the yeast, warm water, and ½ cup flour until smooth.
Cover and let rest in a warm place for 1–12 hours, until bubbly and doubled in size.
In a large bowl, combine the warm milk, sugar, and salt.
Stir in the prepared starter.
Gradually add the remaining flour and melted butter. Mix until a soft, slightly sticky dough forms.
Knead for 8–10 minutes until smooth and elastic.
Place in a lightly greased bowl, cover, and let rise for 1–2 hours, until doubled in size.
Roll or pat the dough to about ½-inch (1.25cm) thickness.
Cut into rounds using a 3-inch (7.5cm) cutter.
Sprinkle cornmeal onto a tray and place the muffins on top. Sprinkle a little more cornmeal over them if desired.
Cover and let rise for 30 minutes.
Heat a skillet or griddle over medium-low heat.
Cook the muffins for 5–7 minutes per side, until golden brown and cooked through.
Transfer to a wire rack and cool completely.
Split each muffin with a fork to preserve the signature nooks and crannies.
Toast and serve with butter, jam, or your favorite toppings.