In a pyrex measuring cup, combine 1 ½ cups of milk. Microwave in 15 seconds burst, and check the temperature with a probe thermometer. The ideal temperature is between 105 °-115° F. Add in 1 tablespoon of yeast and stir. Let sit for 10 minutes, or until yeast starts to bubble.
Whisk 1 egg in a small bowl. Combine with the room temperature butter to the yeast mixture.
In the stand mixing bowl, combine flour, salt, and sugar. With the dough hook attachment, give it a quick mix. With the mixer on low, slowly add the wet ingredients. Turn the mixer up to medium speed and knead the dough for 10 minutes.
Spray a large bowl with cooking spray and place the English muffin dough inside. Cover and proof in a warm spot for 2 hours or refrigerate overnight.
Dust your counter with flour and deflate the dough. Portion dough into 12 equal portions and roll into balls. Grab a baking pan and sprinkle with cornmeal so the muffins won't stick. Place English muffins on a baking tray and flatten with your hand, so they look like pucks. Sprinkle the tops with more cornmeal.
Grab a cast-iron skillet and cook English muffins with a tiny bit of butter. Cook on medium-low heat for 6 minutes per side.
Use a fork to split open the muffins and serve warm.