1. Mixing the Dough: In a large bowl, combine the active sourdough starter, warm water, bread flour, 10 grams of salt, and 1 tablespoon of sugar or malt powder. Mix with a spoon or your hands until a shaggy dough forms and no dry flour remains. Cover the bowl with a damp cloth or plastic wrap and let it rest for 30 minutes (autolyse).

2. Developing the Dough: After the rest, knead the dough on a lightly floured surface for 8-10 minutes until it becomes smooth and elastic. Alternatively, use a stand mixer with a dough hook on medium speed for 5-7 minutes. Place the dough back in the lightly oiled bowl, cover, and let it bulk ferment at room temperature for 4-8 hours, performing 2-3 sets of stretch and folds during the first 2 hours. The dough should become slightly puffy.

3. Shaping the Bagels: Gently turn the dough out onto a lightly floured surface. Divide it into 8-10 equal pieces (about 100-120 grams each). Roll each piece into a tight ball, then use your thumb to poke a hole through the center. Gently stretch the hole to about 1-1.5 inches in diameter, trying to keep the bagel even in thickness. Place the shaped bagels on a parchment-lined baking sheet.

4. Cold Fermentation (Overnight Proof): Cover the baking sheet loosely with plastic wrap and refrigerate the bagels for 8-12 hours, or overnight. This slow, cold fermentation develops deeper flavor and a chewier texture.

5. Prepare for Boiling and Baking: Preheat your oven to 425 F (220 C) with a baking stone or inverted baking sheet inside, if you have one, to ensure a crispy bottom. Bring a large pot of water to a rolling boil. Add the baking soda and the remaining 2 tablespoons of sugar or malt powder to the boiling water. Line another baking sheet with parchment paper.

6. Boiling and Topping: Carefully drop 2-3 bagels into the boiling water at a time, ensuring they don’t overcrowd the pot. Boil for 30-60 seconds per side. The longer they boil, the chewier they will be. Remove them with a slotted spoon, letting excess water drain, and place them on the prepared baking sheet. Brush the tops of the boiled bagels with the lightly beaten egg white and generously sprinkle with the everything bagel seasoning.

7. Baking the Bagels: Transfer the baking sheet with the topped bagels to the preheated oven. Bake for 18-25 minutes, or until golden brown and cooked through. If using a baking stone, carefully transfer the bagels directly onto the stone. Rotate the baking sheet halfway through baking for even browning.

8. Cooling and Serving: Once baked, transfer the bagels to a wire rack to cool completely. This cooling period is crucial for the texture to set. Enjoy them warm or at room temperature.