Add the the sourdough starter and sugar to the bowl of your standing mixer. In a small saucepan, cook butter, milk and water over low heat just until butter is melted. (Or you can microwave it for about 55 seconds.) Either way, cool for five or so minutes before adding it to the ingredients in the bowl of your mixer. (You don’t want it to be super hot.) Blend well with your mixer on low speed.
Add the flour and salt to the mixer and, using the dough hook, start mixing on low speed to incorporate the ingredients. Once the ingredients are well incorporated, continue to blend on medium speed for about 6 minutes longer. The dough will be very moist and soft.
Remove the bowl from the mixer and scrape the dough stuck to the edges of the bowl towards the main body of dough. Cover the top of the bowl with a damp cloth and allow to bulk ferment for 8-10 hours in a warm, draft-free area, but not in the oven. Caveat: I do use the oven but only because I have a “proof” setting. If you have this, it works perfectly, but otherwise, leave the dough on the counter in a warm area. The dough should be doubled in size and very puffy at the end of the fermentation period. This can be done overnight, so you’re ready to shape the English muffins and allow for final proofing in the morning.
Line a baking sheet with parchment paper and distribute the corn meal evenly across the paper. Set aside.
Sprinkle flour on a pastry cloth or cutting board and gently lift the dough from the bowl onto this surface. (Sometimes wetting your hands with a little bit of water makes it easier to handle the dough.) Let rest for about 15 minutes. Then, flatten the dough into a circle about 3/4-inch tall. Using a 4-inch biscuit cutter or a glass with a 4-inch opening, (dip the cutter into flour before each English muffin you cut), cut the dough into your English muffins. Gather any leftover dough into a flatten ball and continue to cut muffins until all dough has been used.
Place cut English muffins on the prepared baking sheet. Cover English muffins with a light, dry towel. Allow to rise for 1 hour more. They don’t rise a lot at the point but will get a bit puffy.
Heat a griddle over medium heat on the stove top. Spray with cooking spray or brush lightly with oil or melted butter. Place muffins on the griddle and cook for about 7-8 minutes per side, or until the muffins are puffy and cooked through and the tops and bottoms are golden brown. Remove muffins from griddle and cool.
Once cooled, fork split the muffins (to make them authentic and easier to cut when ready to serve) and then either toast to eat right away, or store in an airtight container in the refrigerator or freezer until ready to serve. Always split the muffins for cooking using a fork instead of a knife. This is what allows for the nubby texture, which makes delicious little pockets for butter and jam.