Step 1

In a small bowl, whisk together the warm water, sugar, and yeast. Let sit for about 5 minutes, until foamy and the yeast is activated.

Step 2

In a separate large bowl, add the potato starch, cornstarch, millet flour, brown rice flour, psyllium husk powder, salt, and xanthan gum. Whisk to combine.

Step 3

Add the olive oil and egg whites to the yeast mixture and whisk to incorporate.

Step 4

Add the wet ingredients to the bowl of dry ingredients, then whisk vigorously until completely smooth. The dough will be very wet, almost like batter.

Step 5

Line a perforated double-baguette pan with parchment paper. (Tip: Use one long piece of parchment paper and fold it in half with a strong crease that straddles the central 'peak' of the double baguette pan.)

Step 6

Divide the dough evenly between the two halves of the baguette pan, taking care to keep the dough a few inches away from the ends of the pan. It will spread as it rises.

Step 7

Set in a warm location and let rise for 30 minutes, until approximately doubled in volume. (If possible, cover the loaves during the rise, such as with a large inverted cake pan, but make sure it won't touch the rising loaves.) Meanwhile, preheat your oven to 500º F.

Step 8

Bake the loaves for 5 minutes at 500º. Then reduce the oven heat to 375º F and bake for an additional 25 minutes.

Step 9

Remove the loaves from the parchment-lined baguette pan and finish baking for 7 more minutes directly on the oven rack. Then transfer to a wire rack and let cool before slicing.