01 - In a large bowl, combine the active sourdough starter, lukewarm water, and sugar. Stir continuously until the sugar completely dissolves 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 and no dry flour remains visible.
03 - Turn the dough onto a lightly floured surface and knead for 8 to 10 minutes. During the final minute of kneading, work in the vegetable oil until the dough becomes smooth, elastic, and slightly tacky to the touch.
04 - Gently fold the fresh or frozen raspberries into the dough, handling minimally to keep the berries as whole as possible. The dough will appear sticky and have a marbled pink appearance.
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 to 8 hours until doubled in size.
06 - Turn the risen dough onto a lightly floured surface. Using a bench scraper or knife, divide the dough into 8 equal portions, approximately 4 ounces each.
07 - Shape each portion into a smooth ball by tucking the edges underneath. Poke your thumb through the center of each ball and gently stretch to form a 2-inch hole, creating the classic bagel shape.
08 - Arrange shaped bagels on a parchment-lined baking sheet, leaving space between each. Cover with a clean towel and let proof for 1 to 2 hours at room temperature, or refrigerate overnight for deeper flavor development.
09 - Preheat your oven to 425°F with the rack positioned in the center.
10 - Bring 12 cups of water to a rolling boil in a wide, deep pot. Stir in the honey and baking soda (if using) until fully dissolved.
11 - Working in batches of 2 or 3, carefully drop the bagels into the boiling water. Boil for 45 to 60 seconds per side, then remove using a slotted spoon and return to the parchment-lined baking sheet.
12 - While the bagels are still wet from boiling, sprinkle Demerara sugar or poppy seeds evenly over the tops if desired, pressing gently to adhere.
13 - Bake for 22 to 25 minutes until deeply golden brown with a glossy crust, rotating the baking sheet halfway through for even browning.
14 - Transfer the baked bagels to a wire rack and let cool completely for at least 30 minutes before slicing and serving.