How to Make It
Using a wooden spoon, stir together 4 cups of the bread flour, 2 1/2 cups of the water, and 1 1/4 teaspoons of the yeast in a heavy-duty electric stand mixer fitted with the dough hook attachment. Cover loosely with plastic wrap, and let stand at room temperature until very bubbly, about 3 hours.
Add salt, gluten, syrup, 3 cups of the flour, and remaining 1/2 teaspoon yeast to flour mixture. Beat on low speed just until combined. Increase speed to medium-low; beat, gradually adding remaining 1 cup flour, until a very stiff dough forms, about 6 minutes.
Divide dough into 12 balls (about 4 1/4 ounces each). Place dough balls on a lightly floured work surface, and cover with a damp towel. Let stand 20 minutes. Roll 1 dough ball into a 10-inch rope. Overlap ends by 2 inches; press ends together, and roll to form a ring. Place on a lightly greased parchment paper-lined baking sheet. Repeat with remaining dough balls, and a second lightly greased parchment-lined baking sheet. Lightly grease tops of bagels, and cover tightly with plastic wrap. Let stand 20 minutes. Transfer to refrigerator, and chill 8 hours or overnight.
Preheat oven to 500°F with pizza stone on middle oven rack. (Do not remove pizza stone while oven preheats.) Whisk together egg and remaining 1 tablespoon water; set aside.
Fill a large stockpot with water, and bring to a boil over high. Add baking soda. Remove 1 baking sheet of bagels; place bagels in boiling water. Boil 1 1/2 minutes per side. Meanwhile, dust same parchment-lined baking sheet with cornmeal. Transfer boiled bagels to prepared baking sheet; lightly brush with egg wash, and sprinkle with desired toppings. Place baking sheet in oven on preheated pizza stone. Bake 6 minutes. Decrease oven temperature to 450°F, and bake until golden brown, 7 to 9 minutes. Transfer bagels to a wire rack; cool at least 15 minutes. Increase oven temperature to 500°F, and repeat cooking procedure with remaining bagels.