Katarina Cermelj’s Gluten-Free Cheesy Garlic Pull-Apart Bread

Name: Katarina Cermelj’s Gluten-Free Cheesy Garlic Pull-Apart Bread
Cuisine: American
Ingredients: 15 grams (3 tablespoons) whole psyllium husk (Note 1); 180 grams (¾ cup) lukewarm water; 160 grams (1⅓ cups + 1 tablespoon) tapioca starch (Note 2); 135 grams (1 cup) millet flour, plus extra for flouring the surface (Note 3); 25 grams (3 tablespoons) sorghum flour (Note 4); 25 grams (2 tablespoons) caster (superfine) or granulated sugar; 6 grams (2 teaspoons) instant yeast (Note 5); 6 grams (1½ teaspoons) baking powder; 5 grams (2 teaspoons) xanthan gum; 5 grams (1 teaspoon) salt; 100 grams (⅓ cup + 1½ tablespoons) whole milk, lukewarm; 1 medium egg, room temperature; 35 grams (2½ tablespoons) unsalted butter, melted, plus optional 1 to 2 tablespoons (melted), to finish; Flaky salt (optional); 55 grams (½ stick) salted butter, softened; 1 to 2 teaspoons garlic powder; 2 tablespoons finely chopped fresh herbs, such as parsley, rosemary, and oregano; ¼ teaspoon pepper; 80 grams (¾ cup) coarsely grated (shredded) cheddar; 80 grams (¾ cup) coarsely grated (shredded) low-moisture mozzarella