Make the yeast mixture. Warm the milk to about 100°F (38°C). Stir in the sugar and dry yeast, then cover and let it sit for 10 minutes until foamy.
Make the dough. In the bowl of a stand mixer fitted with the dough hook attachment, combine the flour and salt. Add the yeast mixture, melted butter (not hot), and egg to the flour mixture.
Mix on low speed for 2–3 minutes until the dough starts coming together. The dough will look quite sticky at first — this is completely normal. If needed, add just enough extra flour until the dough is no longer overly sticky. I usually end up adding about 2–3 tablespoons.
Increase the mixer speed to medium-low and knead the dough for another 5 minutes until smooth and elastic.
Let the dough rise. Shape the dough into a ball, place it in a lightly greased bowl, cover, and let it rise for about 1 hour or until doubled in size.
Form the dough into muffins. Transfer the dough to a lightly floured surface and divide it into 10 equal portions. Roll pieces lightly between your hands to make balls.
Lightly sprinkle 1 tablespoon of cornmeal over a parchment-lined baking sheet. Place the dough balls on top, then gently press them down with the palm of your hand until they are about 3/4-inch thick.
Carefully cover with a kitchen towel to let rest for 20 minutes.
Cook the muffins. Heat a skillet over medium-low heat. Carefully place the muffins into the pan, leaving a little space between each one so they cook evenly. Depending on the size of your skillet, you may need to cook them in batches. Cover with a lid and cook for about 5 minutes per side, until lightly golden and toasted.
Preheat your oven to 350°F (177°C).
Transfer the muffins to a parchment-lined baking sheet and bake in the preheated oven for about 10 minutes, or until an instant-read thermometer inserted into the center reads 200°F (93°C).
Cool the muffins. Remove from the oven and cool for 10 minutes on the baking sheet before slicing and handling.