3¼ cups (455g) all-purpose gluten-free flour, plus more by the tablespoon
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Scant ½ cup (43g) cultured buttermilk blend powder (I use Saco brand) (you can substitute ? cup (43g) whey powder or the same amount dry milk powder by weight)
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3 teaspoons instant (breadmaker or rapid-rise) yeast
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¼ teaspoon cream of tartar
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¼ teaspoon baking soda
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1 tablespoon (13g) brown sugar
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1 teaspoon kosher salt
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1 teaspoon apple cider vinegar
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2 tablespoons (28g) unsalted butter, at room temperature
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2 extra-large egg whites
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1½ cups warm water (about 105 degrees)
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baking soda bath for boiling (6 cups water + 1 tablespoon baking soda + 1 teaspoon salt)
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cornstarch wash (1 tablespoon cornstarch + ½ cup water mixed into a slurry) (optional – helps rolls to crisp)