Levain (optional*). Feed your sourdough starter by adding 50 grams of sourdough to a cup or bowl with 75 grams of flour and 75 grams of water. Allow to sit for 4-8 hours. Note: If you already have an active sourdough starter, you can use 200 grams of that and start right away.
Once your sourdough starter is nice and bubbly, well risen (2-3 times its original level), and active, add the levain (or starter) to a large mixing bowl with the warm water and salt. Stir to combine.
Once the sourdough starter has been mostly incorporated, add half of the all-purpose flour. Stir to combine.
Add the melted and cooled unsalted butter. Stir to combine.
Once the butter has been well combined, a wet dough will have formed, slowly add in the rest of the flour by adding about ⅓ cup at a time. (this prevents flour pockets from forming.).
Once all the flour has been added and is fully incorporated, cover the bowl with a plate, piece of plastic wrap, or a damp towel and allow it to sit for 1 hour. **The dough will be sticky and that’s okay.
Stretch and folds. After it has sat for an hour it’s time to start the stretch and folds. Before you start, wet your hands with water. This will prevent the dough from sticking to your hands. Start by grabbing one side of the dough, and stretch it up and over the dough. Repeat this process 3 or 4 times or until all corners of the dough have been removed from the sides of the bowl. Turn the dough over so the bottom is facing up.
Cover and allow to sit for 30 minutes.
Repeat the stretch and fold session 3 more times or 4 times total.
Bulk ferment. After the last stretch and fold session allow the dough to rise for 10-12 hours (overnight works best for most) this is the bulk rise. Note: If your kitchen is very warm, this may take just 8-10 hours. If needed for timing, you can do half of your bulk rise at room temperature, and then add it to the refrigerator to cold ferment for another 6-8 hours.
After the bulk rise has finished, the dough should have doubled in size and you should see some bubbles that have formed on the surface.
Divide the dough. Turn the dough out onto a clean, lightly floured surface. If the dough is very sticky, add a little flour until it is easy enough to work with, but still tacky. Separate the dough into 12 equal pieces and form into balls (roughly 102-103 grams each).
Preheat the oven to 375ºF (190ºC).
Line a baking sheet with a piece of parchment paper and set aside.
Prepare an electric skillet by heating it to 375ºF (190ºC). If you’re using the stovetop, I recommend using a cast iron skillet. Heat the skillet on the stovetop over medium heat for about 3-4 minutes, or until it radiates heat.
Add the cornmeal to a shallow bowl or plate. Set aside.
Shape the dough balls into a disc shape and gently press the dough into the cornmeal on both sides.
Transfer to the preheated skillet or griddle and cook for 3-5 minutes. Flip the muffin over after 3-5 minutes and cook for another 2-3 minutes, or until both sides are golden brown.
Once finished, transfer to the prepared baking sheet.
Bake the English muffins at 375ºF (190ºC) for 12-16 minutes, or until your english muffins reach an internal temperature of 200ºF (94ºC) in the center.
Remove them from the oven and allow them to cool for at least 30 minutes before serving. Open them by perforating around the edges with the tines of a fork, then gently pry them open or slice with a serrated knife.