01 - In a large bowl, combine active sourdough starter, lukewarm water, and sugar. Stir continuously until sugar completely dissolves and mixture is uniform.
02 - Add bread flour, whole wheat flour, and sea salt to the starter mixture. Mix with a wooden spoon until shaggy dough begins to form and no dry flour remains visible.
03 - Transfer dough to lightly floured surface. Knead firmly 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 minimal pressure to maintain whole berry integrity. Dough will appear sticky with pink marbling throughout.
05 - Place dough in a greased bowl, cover tightly with plastic wrap, and let rise at room temperature for 6 to 8 hours until doubled in volume.
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 center of each ball to create a hole. Gently stretch and rotate dough to form evenly sized bagel ring with 2-inch center opening.
08 - Arrange bagels on parchment-lined baking sheet, cover with clean kitchen towel. Proof at room temperature for 1 to 2 hours or refrigerate overnight for deeper sourdough flavor development.
09 - Preheat oven to 425°F with rack positioned in center.
10 - Bring 12 cups water to rolling boil in a wide pot. Stir in honey or barley malt syrup until dissolved. Add baking soda now if using for enhanced chewiness.
11 - Working in batches, carefully lower bagels into boiling water. Boil for 45 to 60 seconds per side. Remove using slotted spoon, allowing excess liquid to drain, then return to parchment-lined baking sheet.
12 - Immediately sprinkle Demerara sugar or poppy seeds over wet bagel surfaces while coating from boiling bath is still present.
13 - Bake for 22 to 25 minutes until golden brown with deep color on exposed surfaces. Internal temperature should reach 200°F.
14 - Transfer baked bagels to wire rack. Cool completely for at least 30 minutes before slicing or serving to ensure proper crumb structure sets.