01 - In a large bowl, combine active sourdough starter, lukewarm water, and sugar. Whisk until completely dissolved and mixture appears uniform.
02 - Add bread flour, whole wheat flour, and sea salt to the starter mixture. Mix thoroughly until a shaggy, cohesive dough forms with no dry flour remaining.
03 - Transfer dough to a lightly floured work surface. Knead for 8-10 minutes until smooth and elastic. Add vegetable oil during the final minute of kneading, incorporating completely.
04 - Gently fold fresh raspberries into the dough, working carefully to keep berries intact. Expect a slightly sticky, marbled texture.
05 - Place dough in a lightly oiled bowl, cover with plastic wrap or a damp cloth, and let rise at room temperature for 6-8 hours until doubled in volume.
06 - Turn risen dough onto a floured surface. Divide into 8 equal portions using a dough scraper. Shape each into a ball, then create a center hole with your thumb and gently stretch to form a bagel shape.
07 - Arrange shaped bagels on a parchment-lined baking sheet. Cover with a clean towel and proof for 1-2 hours at room temperature, or refrigerate overnight for deeper flavor development.
08 - Heat oven to 425°F (220°C), positioning rack in the center.
09 - Bring 3 quarts water to a rolling boil in a wide pot. Stir in honey or barley malt syrup and baking soda if using.
10 - Working in batches of 3-4, boil bagels for 45-60 seconds per side. Remove with a slotted spoon, allowing excess water to drain, and return to prepared baking sheet.
11 - While bagels are still damp, sprinkle with Demerara sugar or poppy seeds as desired.
12 - Bake at 425°F for 22-25 minutes until deeply golden brown. Transfer to a wire rack and cool completely before serving.