1. 1. Combine the Starter and Water: In a large mixing bowl, gently whisk together your active sourdough starter and the warm water until the starter is mostly dissolved and the mixture is cloudy. This ensures even distribution of the starter throughout the dough.

2. 2. Mix the Dough Ingredients: Add the bread flour, salt, and 10 grams of granulated sugar to the wet mixture. Mix with a wooden spoon or your hands until a shaggy dough forms and no dry streaks of flour remain. Cover the bowl with a damp cloth or plastic wrap and let it rest for 30 minutes (autolyse). This step helps the flour hydrate.

3. 3. Perform Stretch and Folds: After the rest, perform a series of stretch and folds. With wet hands, grab a portion of the dough from one side, stretch it upwards, and fold it over itself towards the center. Rotate the bowl a quarter turn and repeat this process 3-4 more times until you’ve worked your way around the dough. Repeat this set of stretch and folds every 30 minutes for 2 hours. The dough will become smoother and more elastic with each set.

4. 4. Bulk Fermentation: After the stretch and folds, cover the bowl and let the dough bulk ferment at room temperature for 2-4 hours, or until it has increased in volume by about 30-50% and feels light and airy. Alternatively, you can place it in the refrigerator for 8-12 hours for a slower, colder fermentation, which can develop more flavor.

5. 5. Shape the Bagels: Turn the dough out onto a lightly floured surface. Divide it into 8-10 equal pieces (about 100-120 grams each). Shape each piece into a tight ball, then poke a hole through the center with your thumb and gently stretch the hole to about 1-1.5 inches in diameter. Place the shaped bagels on a parchment-lined baking sheet, leaving some space between them.

6. 6. Proof the Bagels: Cover the baking sheet loosely with plastic wrap or a damp cloth and let the bagels proof at room temperature for 1-2 hours, or until they feel slightly puffy. For best results, cold proofing overnight in the refrigerator (8-12 hours) is highly recommended. This firms up the bagels, making them easier to handle and contributing to a better crust.

7. 7. Boil and Bake: Preheat your oven to 425 F (220 C) with a baking stone or inverted baking sheet inside. Bring a large pot of water to a rolling boil, then add the 2 tablespoons of granulated sugar and the baking soda. 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. Using a slotted spoon, remove the bagels, drain excess water, and place them back on the parchment-lined baking sheet. Sprinkle generously with sesame seeds.

8. 8. Final Bake: Transfer the baking sheet to the preheated oven. Bake for 18-25 minutes, or until the bagels are golden brown and sound hollow when tapped on the bottom. Let them cool on a wire rack before slicing and serving.