In the bowl of a stand mixer fitted with the paddle attachment, place the flour blend, xanthan gum, tapioca starch, sugar, and yeast in a large bowl and whisk to combine well. Add the salt and whisk again.

Add the milk, apple cider vinegar, egg white, and oil, and mix to combine well.

Turn the mixer up to medium-high speed, and mix for about 3 minutes or until the dough begins to look somewhat “whipped,” like air has been incorporated into it.

The dough will be very sticky and shapeless, but should hold together well.

Transfer the dough to a 2 liter proofing bucket with a tight-fitting lid or a large bowl sealed very tightly. Place in the refrigerator for between 12 hours and 2 days.

Place a 10-inch cast iron skillet over medium heat, or heat a griddle to medium (about 350°F). Lightly grease the skillet.

While the pan or griddle is heating, grease four metal English muffin rings (1-inch tall rings cut from empty aluminum cans also work well) and set them aside.

Remove the bread dough from the refrigerator and scoop a portion of about 1/3 cup (95 grams).

Sprinkle a clean, flat surface liberally with tapioca starch, and place the portion of raw dough on top. Using a VERY light touch, and sprinkling with more tapioca starch as necessary to prevent sticking, shape the dough into a 3-inch disk as illustrated in the how-to video. With floured fingers, pinch together any seams that form on the dough.

Repeat with 3 other portions of dough, and place them all in the hot skillet, as far apart as possible (make only 3 at a time if that’s all that fits comfortably). Place the prepared rings around each muffin.

Cover the skillet or the portion of your griddle that your muffins occupy and allow them to cook for at least 10 minutes or until browned on the bottom and the sides seem mostly set (they will no longer glisten).

Uncover the skillet, and remove the rings (unless they’re stuck to the edges of the muffins). Use a spatula to flip the muffins over, and replace the rings.

Cover the skillet again, reduce the heat to medium, and finish cooking until browned on both sides and fully cooked inside (another 15 minutes) The muffins will register at least 200°F on an instant read thermometer placed in the center.

Remove the muffins from the skillet and place on a wire rack to cool briefly until just warm, but no longer hot, to the touch.

Remove the rings, and repeat with the remaining dough, re-using the same muffin rings, newly greased.

Split each muffin with a fork by inserting the tines in the center of the muffin along the middle, parallel to the muffin itself, and gently pry open the muffin with your fingers. Serve warm. With butter. Lots of butter.