01 - In a large bowl, combine the active sourdough starter, lukewarm water, and sugar. Stir continuously until the sugar completely dissolves and the mixture is uniform.
02 - Add bread flour, whole wheat flour, and sea salt to the starter mixture. Stir with a wooden spoon or your hands until a shaggy, rough dough forms.
03 - Turn the dough onto a lightly floured work surface. Knead vigorously for 8 to 10 minutes until the dough becomes smooth and elastic. Drizzle the vegetable oil over the dough during the final minute of kneading and work it in until fully incorporated.
04 - Gently fold the raspberries into the dough using minimal pressure to keep the berries as whole as possible. The dough will become sticky and will have a marbled appearance.
05 - Place the dough in a lightly 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 the risen dough onto a lightly floured surface. Divide into 8 equal portions using a dough scraper or sharp knife.
07 - Form each portion into a smooth ball by tucking the edges underneath. Poke a hole through the center of each ball with your finger, then gently stretch and widen the opening to create the classic bagel shape.
08 - Arrange the shaped bagels on a parchment-lined baking sheet, leaving space between them. Cover with a clean kitchen towel and let proof for 1 to 2 hours at room temperature. For deeper flavor development, refrigerate overnight instead.
09 - Preheat the oven to 425°F.
10 - Bring 12 cups of water to a rolling boil in a wide, deep pot. Stir in the honey or malt syrup until dissolved. Add baking soda now if using for extra chewiness.
11 - Working in batches, carefully lower 2 to 3 bagels into the boiling water. Boil for 45 to 60 seconds, then flip and boil the second side for another 45 to 60 seconds. Remove with a slotted spoon, allowing excess water to drain off, and return to the baking sheet.
12 - Immediately sprinkle the wet bagels with Demerara sugar or poppy seeds if desired. The water helps the toppings adhere.
13 - Bake for 22 to 25 minutes until the bagels are deeply golden brown and sound hollow when tapped on the bottom.
14 - Transfer the baked bagels to a wire rack and let cool completely before slicing and serving.