Prepare the buttermilk. In the microwave or on the stovetop, heat 1 1/2 cups of buttermilk to 105 degrees. In a standing mixer fitted with the dough hook, add remaining cold buttermilk. In the standing mixer with the cold buttermilk, pour in the warm buttermilk followed by the yeast, butter, honey, bread flour, sugar, and salt.
Mix dough. Mix ingredients on low for 1 minute, then increase speed and continue mixing for another 2 minutes until a sticky but smooth dough forms.
Let dough rise in the fridge. Put the dough in a greased bowl, cover with plastic wrap and chill in the fridge for one hour.
Prepare baking sheets and work surfaces. Line two sheet pans with parchment paper, sprinkle 1/4 cup of the cornmeal, and set aside. Sprinkle half of the remaining cornmeal on a sanitized work surface.
Shape dough. After an hour, remove dough from the fridge and place it on a clean work surface. Turn the dough and sprinkle the top with remaining cornmeal. Press the dough out to about a 1-inch thickness. Use a 3-inch round cutter to cut out the rounds, cutting out as many as possible (dough can not be pressed back out).
Let dough rise again. Place the muffins on the sheet pan, 1" apart, cover with plastic wrap and let rise at room temperature for one hour.
Bake homemade English muffins. Preheat oven to 350°. Once preheated, heat a griddle or cast-iron skillet on medium-high heat. Place the muffins in the hot pan. Cook muffins, one minute per side, until golden brown. Arrange the par-cooked muffins on the sheet pans and bake for 8 to 10 minutes. Depending on the size of your skillet, you may need to work through this step in batches.