01 - In a large bowl, whisk together the active sourdough starter, lukewarm water, and sugar until completely dissolved.
02 - Add bread flour, whole wheat flour, and sea salt to the starter mixture. Stir with a wooden spoon until a shaggy, sticky dough forms.
03 - Turn dough onto a lightly floured surface. Knead for 8 to 10 minutes until smooth and elastic, drizzling in the vegetable oil during the final 2 minutes.
04 - Gently fold in the raspberries by hand, taking care to keep them as whole as possible. The dough will appear sticky and slightly marbled.
05 - Place dough in a 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 risen dough onto a floured surface. Divide into 8 equal portions using a dough scraper or knife.
07 - Form each portion into a smooth ball. Poke a hole through the center with your finger and gently stretch to create a 2-inch opening, forming the classic bagel shape.
08 - Arrange bagels on a parchment-lined baking sheet. Cover with a towel and let proof for 1 to 2 hours at room temperature, or refrigerate overnight for deeper flavor development.
09 - Preheat oven to 425°F.
10 - Bring 12.5 cups of water to a rolling boil in a wide pot. Stir in honey or barley malt syrup and baking soda if using.
11 - Working in batches, carefully drop bagels into boiling water. Boil for 45 to 60 seconds per side. Remove with a slotted spoon, drain briefly, and return to the baking sheet.
12 - Immediately sprinkle boiled bagels with Demerara sugar or poppy seeds if desired, while surfaces are still tacky.
13 - Bake for 22 to 25 minutes until deeply golden brown and crisp. Transfer to a wire rack and cool completely before slicing or serving.