01 - Combine active sourdough starter, lukewarm water, and sugar in a large mixing bowl. Stir until sugar completely dissolves.
02 - Add bread flour, whole wheat flour, and sea salt to the starter mixture. Mix 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. Drizzle vegetable oil onto dough during the final minute of kneading and work it in.
04 - Gently fold raspberries into the dough, handling carefully to keep berries as whole as possible. Dough will appear sticky and slightly marbled with pink juice.
05 - Place dough in a 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 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 classic bagel shape.
08 - Arrange bagels on a parchment-lined baking sheet. Cover with a clean towel. Let proof at room temperature for 1 to 2 hours, or refrigerate overnight for deeper sourdough flavor.
09 - Preheat oven to 425°F.
10 - Bring 12 cups water to a rolling boil in a wide pot. Stir in honey or barley malt syrup, plus baking soda if using for extra chew.
11 - Working in batches, carefully lower bagels into boiling water. Boil for 45 to 60 seconds per side. Remove with a slotted spoon, allowing excess water to drain, and return to baking sheet.
12 - Immediately sprinkle boiled bagels with Demerara sugar or poppy seeds while surfaces are still tacky, if desired.
13 - Bake for 22 to 25 minutes until deep golden brown. Transfer to a wire rack and cool completely before slicing or serving.