01 - Combine active sourdough starter, lukewarm water, and sugar in a large mixing bowl. Whisk until sugar completely dissolves and mixture is uniform.
02 - Add bread flour, whole wheat flour, and sea salt to the starter mixture. Stir with a wooden spoon until shaggy dough forms and no dry flour remains visible.
03 - Turn dough onto lightly floured surface and knead for 8 to 10 minutes until smooth and elastic. Drizzle with vegetable oil during the final minute of kneading and work until fully incorporated.
04 - Gently fold fresh raspberries into the dough using minimal pressure to keep berries intact. The dough will become sticky and display a marbled appearance.
05 - Place dough in a lightly greased bowl, cover with plastic wrap or damp towel, and let rise at room temperature for 6 to 8 hours until doubled in size.
06 - Turn risen dough onto lightly floured surface. Divide into 8 equal portions using a bench scraper or sharp knife.
07 - Roll each portion into a smooth ball. Press thumb through the center to create a hole, then gently stretch and rotate to form an even ring with approximately 2-inch diameter opening.
08 - Arrange shaped bagels on parchment-lined baking sheet, cover with clean towel, and proof for 1 to 2 hours at room temperature. Alternatively, refrigerate overnight for deeper sourdough flavor development.
09 - Position oven rack to center position and preheat to 425°F.
10 - Bring 3 quarts water to a rolling boil in a wide pot. Stir in honey or barley malt syrup and baking soda if using until dissolved.
11 - Working in batches of 2 to 3, boil bagels for 45 to 60 seconds per side. Remove using a slotted spoon, allowing excess liquid to drain, and return to parchment-lined baking sheet.
12 - Sprinkle wet bagels immediately with Demerara sugar or poppy seeds while surface is still tacky to ensure adherence.
13 - Bake for 22 to 25 minutes until bagels develop deep golden-brown crust. Transfer to wire rack and cool completely before slicing or serving.