01 - Combine active sourdough starter, lukewarm water, and sugar in a large mixing bowl. Stir continuously until sugar completely dissolves and mixture is uniform.
02 - Add bread flour, whole wheat flour, and sea salt to starter mixture. Mix with wooden spoon until shaggy dough forms and no dry flour remains visible.
03 - Turn dough onto lightly floured work surface. Knead for 8 to 10 minutes until smooth and elastic. Drizzle vegetable oil over dough during final minute of kneading and work until fully incorporated.
04 - Gently fold raspberries into dough using stretch-and-fold technique. Handle minimally to keep berries whole, creating marbled appearance. Dough will remain sticky.
05 - Place dough in 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 lightly floured surface. Divide into 8 equal portions using bench scraper or knife.
07 - Form each portion into smooth ball by tucking edges underneath. Poke thumb through center to create hole. Gently stretch and rotate to form uniform ring with 2-inch diameter.
08 - Arrange bagels on parchment-lined baking sheet. Cover with clean towel and proof at room temperature for 1 to 2 hours until visibly puffed. Alternatively, refrigerate overnight for deeper sourdough flavor development.
09 - Set oven to 425°F approximately 30 minutes before baking.
10 - Bring 12 cups water to rolling boil in wide pot. Stir in honey and baking soda if using until dissolved.
11 - Working in batches of 2 or 3, lower bagels into boiling water. Cook 45 to 60 seconds per side until surface appears slightly set and glossy. Remove with slotted spoon, allowing excess water to drain.
12 - Immediately transfer boiled bagels back to parchment-lined baking sheet. Sprinkle with Demerara sugar or press into poppy seeds while surface is still moist for adherence.
13 - Bake for 22 to 25 minutes until deep golden brown, rotating baking sheet halfway through for even coloring.
14 - Transfer baked bagels to wire rack. Cool completely for at least 30 minutes before slicing or serving to ensure proper texture set.