In a large bowl, mix 500g bread flour with 323g filtered water until no dry spots remain. Cover and let rest for 45 minutes to hydrate the flour and improve dough extensibility.

Add 100g active sourdough starter and 10g salt to the dough. Mix well by pinching and folding until fully combined. The dough will be sticky—this is normal.

Let the dough bulk ferment at room temperature (21–24°C / 70–75°F) for 4–5 hours. Perform 3–4 sets of stretch and folds every 30 minutes in the first 2 hours. Let the dough rest undisturbed for the final 1–2 hours until puffed and slightly domed.

Turn the dough out onto a lightly floured surface. Gently stretch the dough into a rectangle and scatter 150g cream cheese cubes and 150g blueberries across the surface. Carefully fold the dough over itself several times to evenly distribute the inclusions without smashing them.

Shape the dough gently into a loose rectangle and let it rest, covered, for 20 minutes to relax the gluten.

Lightly oil or line your loaf pan with parchment paper. Shape the dough into a tight log and transfer it into the pan seam-side down. Cover loosely with a towel or plastic wrap and let it proof for 1–2 hours at room temperature, or overnight in the fridge (8–12 hours) for enhanced flavor.

Preheat your oven to 230°C (450°F). If the dough was refrigerated, let it warm up for 30–45 minutes before baking. Lightly score the top of the loaf with a sharp knife or bread lame.

Place the loaf pan in the oven and bake for 35–40 minutes, or until the top is golden brown and the internal temperature reaches ~94°C (200°F). Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.