Place the milk in a 4 cup measuring cup or similar sized bowl. Sprinkle the psyllium husk on top and whisk or mix to combine well. Allow the mixture to sit for at least 30 seconds so the psyllium absorbs the moisture and gels.
In the bowl of a stand mixer fitted, place the flour, xanthan gum, tapioca starch, milk powder, yeast, cream of tartar, baking soda, and brown sugar, and whisk to combine well, breaking up any lumps in the brown sugar. Add the salt, and whisk again to combine.
Add the apple cider vinegar, butter, egg whites, and milk with psyllium mixture. Use the paddle attachment or a separate, handheld spatula to mix the dough at low speed or by hand until just combined into a cohesive dough.
You can continue to use the paddle attachment, or scrape the dough off of it and replace it with the dough hook. Turn the mixer speed up to medium-high, and then high speed and beat for 4 more minutes. The dough should start off clumping around the dough hook, and eventually start sticking to the sides of the bowl again.
Let the dough rise, refrigerated
Transfer the dough to a lightly oiled bowl or proofing bucket large enough for it to rise to nearly double its size.
Cover the bowl tightly with an oiled piece of plastic wrap or the oiled top of your proofing bucket. Place it in the refrigerator for at least 1 hour and up to 3 days.
Shape the prepared dough
When the dough is ready, line rimmed baking sheets with unbleached parchment paper and set them aside. Turn the dough out onto a lightly floured surface, sprinkle it lightly with a bit more flour, and turn it over on itself a few times until it’s smoother.
Using a bench scraper or large knife, divide the dough into 8 equal portions, each about 5 ounces, and roll each into a ball.
Working with one piece of dough at a time, and using the palms of both hands lightly pressing away from one another, roll the dough into a thin rope about 12 inches long. As you work on the dough, sprinkle it very lightly with flour to prevent sticking.
Create an upside-down U shape with the dough, and cross the two ends over one another into an X shape 2 to 3 inches away from each end.
Grab each crossed end with the opposite hand, criss-cross them once, then turn them over onto the round end of the original U shape. Press the ends onto the round end to adhere. You can moisten the ends a bit to help them stick as they rise.
Transfer the shaped pretzels to the prepared baking sheets about 2 inches apart from one another. Cover with lightly oiled plastic wrap and set in a warm, draft-free location to rise until nearly doubled in size (about 1 hour). Do not overproof.
Make the (optional) dipping sauce.
Combine all the ingredients in a medium-sized bowl, and whisk to combine well. The dry mustard powder really gives the sauce a nice depth of flavor, but it is entirely optional. Set the sauce aside.
Boil and bake the risen pretzels
As the dough nears the end of its rise, preheat your oven to 400°F.
In a large pot, make the baking soda bath by dissolving the baking soda and salt in approximately 6 cups of water, and bringing it to a rolling boil over medium-high heat.
Once the dough has finished rising, use a bread lame or small sharp knife to score each risen pretzel about 1/8-inch deep in 3 spots: the left arm and right arm, and on the top of the twist at the center.
Place the pretzels a few at a time in the boiling baking soda bath for less than one minute total. Flip gently to invert, and boil for another 30 seconds.
Reinvert the boiled pretzels and use a strainer to remove them from the water, letting excess water drain off into the pan. Return each of them the baking sheet.
Brush each boiled pretzel generously with the melted butter, then sprinkle with coarse salt.
Place the baking sheet in the center of the preheated oven. Bake for 15 minutes at 400°F. Reduce the oven temperature to 350°F, and continue to bake for about 15 minutes more or until dark brown all over and firm to the touch.
Remove from the oven, let cool for 20 minutes before serving with the dipping sauce.
Video
Notes
For the flour blend. I recommend Better Batter’s original blend or my Nicole’s Best multipurpose blend (with added xanthan gum). King Arthur's gluten free bread flour should also work but,add up to 2 tablespoons more milk by the teaspoon as you make the dough, mimicking the texture you see in the photos and video. Avoid Cup4Cup and Measure for Measure here—they won't produce the right texture. Vitacost's multi-blend gluten free flour, with added xanthan gum, should also work. To make your own blend using one of my “mock” recipes, please see the all purpose gluten free flour blends page. I recommend my mock Better Batter. Psyllium husk. You must use higher purity “blond” husk, or your baked goods may turn a harmless but unsightly blue/purple color. I like NaturaleBio brand whole husk from Amazon, but if it's out of stock, I would buy Yupik brand. You can make the dough without the psyllium husk, but will not be as smooth. You must use the paddle attachment on your stand mixer, not the dough hook, and the dough will be more difficult to handle. Add an additional 1 teaspoon xanthan gum to the dry ingredients, and add the milk alone when you add the other wet ingredients. Nutrition information excludes the baking soda bath, melted butter and coarse salt on top, and dipping sauce.