01 - Whisk together the active sourdough starter, lukewarm water, and sugar in a large mixing bowl until the sugar completely dissolves.
02 - Add bread flour, whole wheat flour, and sea salt to the starter mixture. Stir with a wooden spoon or dough whisk until a shaggy, sticky dough forms with no dry flour remaining.
03 - Turn dough onto a lightly floured surface and knead for 8–10 minutes until smooth and elastic. Drizzle in the vegetable oil during the final minute of kneading.
04 - Gently fold the fresh raspberries into the dough using minimal pressure to keep the berries as whole as possible. The dough will become sticky and take on a marbled appearance.
05 - Place dough in a lightly greased bowl, cover with plastic wrap or a damp towel, and let rise at room temperature for 6–8 hours until doubled in size.
06 - Turn risen dough onto a lightly floured surface. Divide into 8 equal portions using a bench scraper or sharp knife, approximately 4 oz each.
07 - Form each portion into a smooth ball by tucking edges underneath. Poke a hole through the center with your finger and gently stretch to form a 2-inch diameter ring.
08 - Arrange bagels on a parchment-lined baking sheet, cover with a clean towel, and proof for 1–2 hours until puffy. For enhanced flavor, refrigerate overnight for 8–12 hours.
09 - Preheat oven to 425°F with oven rack positioned in the center.
10 - Bring 12 cups of 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 2–3, boil bagels for 45–60 seconds per side. Remove with a slotted spoon, allowing excess water to drain, and return to the parchment-lined baking sheet.
12 - Sprinkle the wet bagel tops with Demerara sugar or poppy seeds immediately after boiling while the surface is still sticky.
13 - Bake for 22–25 minutes until bagels are deeply golden brown with a shiny crust. Rotate the baking sheet halfway through for even browning.
14 - Transfer baked bagels to a wire rack and cool for at least 30 minutes before slicing or serving to complete the internal crumb structure.