Before you begin: Confirm your starter is active and bubbly, it should at least double within 4 to 6 hours of its last feeding. Warm your milk to room temperature so it doesn't shock the starter. Plan backwards from when you want to cook, this is roughly a 9 to 10 hour process from first mix to skillet.
In a large bowl, combine the active sourdough starter, warm milk, sugar, melted butter, and honey. Whisk until the starter is fully dissolved.
Add the flour and mix until you form a sticky shaggy dough. Cover with plastic wrap or a tea towel and rest 30 to 60 minutes to hydrate the flour.
Add the salt and mix to combine.
Turn the dough onto a lightly floured surface and knead for about 5 minutes, until smooth and elastic.
Place the dough back in the bowl, cover, and let it bulk ferment in a warm spot until doubled, 8 to 10 hours at 68 to 75º F (overnight).
The next morning, gently turn the dough out onto a floured surface and dust the top with a little flour. Press it out with your fingertips to about ½ inch thick.
Cut into 12 rounds with a 3-inch biscuit cutter (or 3.5-inch english muffin rings). Re-roll scraps gently for the last few.
Place the muffins on a baking sheet lined with parchment dusted with cornmeal. Sprinkle more cornmeal on top, cover with a tea towel, and rise at room temperature for 1 hour.
Preheat a large skillet over LOW heat (around 325º F surface temp). Lightly grease the skillet.
Place 4 muffins in the pan at a time, spaced 2 inches apart. Cover with a lid and cook for 4 minutes on the first side.
Flip and cook another 4 minutes covered. Internal temp should reach 205 to 210º F when done.
Transfer to a wire rack to cool at least 10 minutes before splitting. Use a fork (not a knife) to open them up and preserve the nooks and crannies.
Ingredient notes: Whole milk gives the richest crumb; 2% or plant milk work too. Active starter only, do not substitute discard (the rise depends on the active yeast). Honey adds both sweetness AND browning on the crust, swap with maple syrup or agave for vegan.Equipment notes: HexClad and cast iron give the most even heat. Lighter or thinner skillets run hot and brown the outside before the inside cooks, drop the heat a notch lower than you think you need. English muffin rings (3.5-inch) give Thomas's-style straight edges; a biscuit cutter is fine and gives a slightly more rustic shape.Same-day option: Skip the overnight bulk rise. Instead, let the dough rise in a warm spot (78 to 80º F) for 3 to 4 hours until doubled, then proceed with cutting and second rise. Same-day muffins have a milder tang.Cold-retard for more tang: After the bulk rise, chill the dough in the fridge up to 24 hours before pressing out. The cold deepens the tang and makes the dough easier to handle.Make ahead and storage: Cooled muffins keep airtight at room temperature up to 1 week, in the fridge up to 2 weeks. Freeze sliced (so you can toast from frozen), wrapped in foil + freezer bag, up to 6 months.Vegan version: Plant milk + vegan butter + maple syrup or agave (skip the honey). All other steps stay the same.Baking option (if you don't want to use the stovetop): Bake at 375º F for 15 to 20 minutes, internal temp 190º F. Note: oven-baked muffins won't have the same trapped-bubble nooks and crannies, they'll be more like a small dinner roll than a true english muffin.Critical do-nots:
Don't cook on high heat. The outside will set before the inside cooks, leaving you with gummy centers.
Don't slice with a knife. Use a fork to preserve the nooks and crannies.
Don't substitute regular flour for cornmeal on the pan, it absorbs and you lose the texture.