1. Combine the Wet Ingredients and Starter: In a large mixing bowl, gently whisk together your active sourdough starter and warm water until the starter is mostly dissolved. The mixture should look milky and slightly frothy.

2. Mix the Dough: Add the bread flour, salt, and 10 grams of granulated sugar to the wet mixture. Use a sturdy spoon or your hands to mix until a shaggy dough forms and all the flour is hydrated. It will be sticky at this stage. Cover the bowl with a damp cloth or plastic wrap and let it rest for 30 minutes. This is called autolyse, and it helps the flour absorb water.

3. Knead and Develop the Dough: After the rest, turn the dough out onto a lightly floured surface. Knead the dough for about 8-10 minutes. It will start sticky but become smoother and more elastic as you work it. You should be able to stretch a small piece of dough thin enough to see light through it without tearing (the “windowpane test”). Form the dough into a ball and place it back in the lightly oiled bowl.

4. First Rise (Bulk Fermentation): Cover the bowl and let the dough rise at room temperature for 1-2 hours, performing a “stretch and fold” every 30 minutes. To do this, gently pull a section of the dough up and fold it over itself, rotating the bowl a quarter turn and repeating until you’ve gone all the way around. After the room temperature rise, place the covered bowl in the refrigerator for 8-12 hours (or up to 24 hours) for a slow cold fermentation. This develops the sourdough flavor.

5. Shape the Bagels: The next day, remove the dough from the fridge. It will be firm and slightly puffy. Divide the dough into 8 equal pieces (about 100-110 grams each). Roll each piece into a smooth ball. To create the hole, poke a hole in the center of each ball with your floured thumb and gently stretch the dough to create a 1-inch hole, trying to keep the thickness even around the ring. Place the shaped bagels on a parchment-lined baking sheet. Let them rest at room temperature for 30-60 minutes while you preheat your oven and prepare the water bath.

6. Prepare for Boiling and Baking: Preheat your oven to 425 F (220 C) with a rack in the middle. Bring a large pot of water to a rolling boil. Add 1 tablespoon of granulated sugar and 1 teaspoon of baking soda to the boiling water. This creates the alkaline bath that gives bagels their signature chew and shine.

7. Boil and Bake the Bagels: Carefully drop 2-3 bagels into the boiling water at a time, ensuring they don’t crowd the pot. Boil for 30 seconds to 1 minute per side. They should float and puff up slightly. Using a slotted spoon, remove the bagels from the water, letting excess water drain, and place them back on the parchment-lined baking sheet. If desired, sprinkle with your chosen toppings immediately after boiling.

8. Bake to Golden Perfection: Transfer the baking sheet to the preheated oven. Bake for 18-22 minutes, or until the bagels are golden brown and have a firm, chewy crust. Rotate the baking sheet halfway through baking for even browning. Let them cool on a wire rack before slicing and serving.