1. Make the Sponge

• In a large bowl, mix your ripe sourdough starter with the water until foamy.
• Add the flour and mix until fully incorporated, scraping down the sides of the bowl.
• Cover the bowl loosely with plastic wrap or a lid and let sit at room temperature for 6–8 hours, or until the mixture is foamy and stretchy.
• Test readiness by dropping 1 tsp of the sponge into a glass of cold water—if it floats, it’s ready.

2. Prepare the Final Dough

• Measure out 5 cups (1,000 g) of the prepared sponge. Reserve any extra for another recipe.
• In a large mixing bowl, combine the sponge, salt, malt, yeast, and 3 cups of flour. Mix to form a rough dough.
• Gradually add the remaining 1 cup of flour, 1/4 cup at a time, kneading the dough until it becomes tough, smooth, and non-sticky. Adjust flour or add a few drops of water if needed.

3. Knead the Dough

• Knead by hand or with a dough hook for 10 minutes (15 minutes by hand) until elastic and fully smooth. The dough will be stiff.

4. Portion and Shape the Dough

• Divide the dough into 12 equal portions (approximately 4 1/2 oz or 130 g each for standard-sized bagels).
• Shape each portion into a ball, then roll it into a sausage shape about 8 inches long.
• Form a circle by wrapping the dough around your fingers, overlapping the ends under your index finger. Seal the ends by rolling them together on a flat surface.

5. Rest and Test

• Place the shaped bagels on a parchment-lined baking sheet and cover with plastic wrap. Let them rise for 20 minutes.
• Perform the float test: Place one bagel in a bowl of cold water. If it floats, it’s ready. If it sinks, let the bagels rise for another 15–20 minutes and test again.
• Once ready, cover the bagels and refrigerate them overnight or for up to 36 hours.

6. Boil the Bagels

• Preheat your oven to 500°F (260°C) and prepare a parchment-lined baking sheet.
• Bring a large pot of water to a rapid boil and add 1 tbsp baking soda.
• Working in batches, boil 3–4 bagels at a time for 1 minute per side, flipping them once with a slotted spoon.
• Remove boiled bagels to a clean dish towel to drain.

7. Add Toppings and Bake

• While the bagels are sticky, sprinkle them with your desired toppings.
• Transfer the bagels to the prepared baking sheet and bake for 20–25 minutes, rotating the sheet halfway through if your oven has hot spots. Bagels should be golden brown on all sides.

8. Cool and Enjoy

• Cool the bagels on a wire rack before slicing or storing. Fully cooled bagels can be frozen for up to 3 months.