Day 1: Make the Dough

1. Mix the ingredients: In a large bowl, combine the bread flour, active sourdough starter, warm water, salt, and honey or malt syrup. Mix until a shaggy dough forms.
2. Knead the dough: Transfer the dough to a lightly floured surface and knead for 8-10 minutes until smooth and elastic.
3. Bulk fermentation: Place the dough in a lightly oiled bowl, cover with a damp towel or plastic wrap, and let it rest at room temperature for 4-6 hours, or until it has doubled in size. Then refrigerate overnight for slow fermentation.

Day 2: Shaping and Proofing

4. Divide the dough: Remove the dough from the fridge and divide it into 8 equal pieces (about 100 g each).
5. Shape the bagels: Roll each piece into a ball. Poke your thumb through the center of each ball and gently stretch to form a bagel shape with a 1-2 inch hole in the middle.
6. Final proofing: Place the shaped bagels on a parchment-lined baking sheet. Cover them with a towel and let them proof for 1-2 hours at room temperature, or until puffy but not overly soft.

Boiling and Baking

7. Preheat the oven: Preheat your oven to 220°C (425°F). Place a baking stone or sheet in the oven to heat.
8. Boil the bagels: Bring 2 liters of water to a boil in a large pot. Add honey or malt syrup and baking soda to the water. Gently drop 2-3 bagels at a time into the boiling water and boil for 1 minute per side. Remove with a slotted spoon and place back on the parchment-lined sheet.
9. Add toppings: Sprinkle toppings on the wet bagels, pressing gently to adhere.
10. Bake the bagels: Transfer the bagels to the preheated baking stone or sheet and bake for 20-25 minutes, or until golden brown and firm. Rotate the pan halfway through for even browning.
11. Cool and serve: Let the bagels cool for at least 15 minutes before serving.