Prepare the Dough
In a large bowl, combine the sourdough starter, bread flour, water, salt, blueberry powder, and blue spirulina (if using). Mix until the ingredients are fully incorporated into a sticky dough.

Initial Rest
Cover the bowl and let the dough rest at room temperature for 30 minutes. This rest allows the flour to fully absorb the water and starts gluten development.

Stretch and Fold Method
Over the next two hours, perform a series of four stretch-and-folds—once every 30 minutes. This strengthens the dough without traditional kneading.

Bulk Fermentation
After the final fold, cover the dough again and let it rise in a warm spot for 2 to 3 hours, or until it has increased in volume by about 50%.

Shape the Dough
Line a baking pan with parchment paper and coat it with 2–3 tablespoons of olive oil. Gently transfer the dough into the pan, using your fingertips to stretch it toward the corners. Be careful not to deflate the dough.

Dimple and Oil the Surface
Drizzle 2–4 tablespoons of olive oil over the top of the dough. Using your fingertips, press deeply into the surface to create dimples. These will catch oil and hold the toppings in place.

Prepare the Topping
In a small bowl, toss the blueberries with the sugar until evenly coated. Spread the sugared berries over the dough, gently pressing them in. Sprinkle any remaining sugar across the top—this will help form a caramelized crust as it bakes.

Cold Proof Overnight
Cover the pan and place it in the refrigerator overnight. This slow fermentation improves the dough’s flavor and structure.

Bake from Cold
The next day, preheat your oven to 430°F (220°C). Take the focaccia directly from the fridge and place it into the hot oven—no need to bring it to room temperature. This prevents overproofing and gives the dough a better rise.

Bake and Cool
Bake for 20 to 25 minutes, or until the surface is golden brown and the edges look crisp. Remove from the oven, lift the focaccia from the pan, and transfer it to a wire rack to cool completely.

Let It Set Before Slicing
Wait until the focaccia has fully cooled before slicing. Cutting too soon will release steam, which can make the inside gummy.