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 5 days.
Shape the dough
Place a 10-inch cast iron skillet over medium to medium-low 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.
Sprinkle a clean, flat surface liberally with tapioca starch. Remove the raw dough from the refrigerator, scoop 3 to 4 portions of about 1/3 cup (95 grams), and place them loosely on top of the floured surface.
Using a very light touch, and sprinkling with more tapioca starch as necessary to prevent sticking, shape each piece of dough loosely into a 3-inch round. With floured fingers, pinch together any seams that form on the dough.
Cook the muffins
Place the shaped pieces of dough about 1 inch apart from one another the prepared 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, and finish cooking until browned on both sides and fully cooked inside (another 15 minutes) The muffins will register about 200°F on an instant read thermometer placed in the center.
Remove the rings, then the muffins from the skillet and place on a wire rack to cool briefly until just warm, but no longer hot, to the touch. They will deflate as they cool.
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. Gently pry open the muffin with your fingers. Serve warm.
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Notes
Flour blend choices.My favorite gluten free flour blends are Better Batter's original blend gluten free flour and Nicole's Best multipurpose blend (with 3 teaspoons added xanthan gum). King Arthur Flour's gluten free bread flour would also work here, but would make less fluffy muffins. Their Measure for Measure blend will not work.I don't recommend Bob's Red Mill 1-to-1 Gluten Free Baking Flour in yeast bread. I don't recommend Cup4Cup any more as they've changed the formula.To make your own blend using one of my “mock” recipes, please see the all purpose gluten free flour blends page.