01 - Combine active sourdough starter, lukewarm water, and sugar in a large mixing bowl. Stir until sugar completely dissolves and mixture is uniform.
02 - Add bread flour, whole wheat flour, and sea salt to the starter mixture. Mix with a wooden spoon or hands until a shaggy, rough dough forms and no dry flour remains.
03 - Turn dough onto lightly floured surface. Knead for 8 to 10 minutes until smooth and elastic. Drizzle with vegetable oil during final minute of kneading and incorporate fully.
04 - Gently fold fresh raspberries into dough, handling minimally to keep berries whole. Dough will appear sticky with pinkish marbling throughout.
05 - Place dough in lightly greased bowl, cover with plastic wrap or damp towel. Let rise at room temperature for 6 to 8 hours until doubled in size.
06 - Turn risen dough onto floured surface. Divide into 8 equal pieces using a dough scraper or bench knife.
07 - Form each piece into a smooth ball by tucking edges underneath. Poke thumb through center and gently stretch to create 2-inch hole, forming classic bagel shape.
08 - Arrange bagels on parchment-lined baking sheet. Cover with clean kitchen towel and let proof at room temperature for 1 to 2 hours until puffy. Alternatively refrigerate overnight for deeper flavor development.
09 - Position oven rack to center position. Preheat to 425°F.
10 - Bring 3 quarts water to rolling boil in wide pot. Stir in honey and baking soda if using until dissolved.
11 - Working in batches, carefully lower bagels into boiling water. Boil for 45 to 60 seconds per side. Remove with slotted spoon, drain briefly, and return to prepared baking sheet.
12 - Immediately sprinkle wet bagel tops with Demerara sugar or poppy seeds while surface is still tacky for better adhesion.
13 - Bake for 22 to 25 minutes until deeply golden brown and crusty. Rotate baking sheet halfway through for even browning.
14 - Transfer baked bagels to wire rack. Cool completely for at least 30 minutes before slicing or serving to allow crumb structure to set.