01 - In a large bowl, combine the active sourdough starter, lukewarm water, and sugar. Stir thoroughly until the sugar dissolves completely and the mixture is uniform.
02 - Add bread flour, whole wheat flour, and sea salt to the starter mixture. Mix with a wooden spoon or your hands until a shaggy, rough dough forms.
03 - Turn the dough onto a lightly floured surface. Knead for 8–10 minutes until smooth and elastic. Drizzle the vegetable oil over the dough during the final minute of kneading and work it in until fully incorporated.
04 - Gently fold the raspberries into the dough, being careful to keep them as whole as possible. The dough will become sticky and appear slightly marbled with raspberry juice.
05 - Transfer the dough to a lightly greased bowl, cover with plastic wrap or a damp towel, and let rise at room temperature for 6–8 hours until doubled in size.
06 - Turn the risen dough onto a lightly floured surface. Divide into 8 equal portions using a dough scraper or sharp knife.
07 - Shape each portion into a smooth ball by tucking the edges underneath. Poke a hole through the center of each ball with your finger, then gently stretch and rotate to form an even ring with a 2-inch opening.
08 - Place the shaped bagels on a parchment-lined baking sheet, cover with a clean towel, and let proof for 1–2 hours at room temperature. For enhanced flavor development, refrigerate overnight.
09 - Preheat the oven to 425°F.
10 - Bring 12 cups of water to a rolling boil in a wide, deep pot. Stir in the honey or barley malt syrup, and add the baking soda if using for extra chewiness.
11 - Working in batches of 2–3, carefully lower the bagels into the boiling water. Boil for 45–60 seconds per side, then remove with a slotted spoon and return to the parchment-lined baking sheet, draining well.
12 - Immediately sprinkle the wet bagels with Demerara sugar or poppy seeds if desired, pressing gently to adhere.
13 - Bake for 22–25 minutes until deep golden brown and the crust is firm. Rotate the baking sheet halfway through for even browning.
14 - Transfer the baked bagels to a wire rack and cool completely before slicing or serving.