Prepare the Dough (Night Before Baking):In a large mixing bowl, combine 100g active sourdough starter, 375g filtered water, and 30g honey- stir until milky. Then, add 500g unbleached bread flour and 10g salt, mixing until the dough comes together. Cover and let the dough rest for 30 min to 1 hour.
Stretch and fold and Bulk Ferment: Perform 2-3 of sets of stretch and folds 30 minutes apart to develop gluten structure. Let the dough bulk ferment at room temperature overnight (8–12 hours). This step is very forgiving—even an over-proofed dough can still create a fantastic focaccia!
Baking the Focaccia (Next Morning): Preheat your oven to 425°F (218°C).
In a small bowl, melt 1 stick of butter. Use a portion of this melted butter to grease a 9×13” baking pan or 12" cast iron skillet. Then, stir ¼ cup sugar and the zest of 2 lemons into the butter.
Transfer the dough into the greased baking pan, gently stretching it to cover the bottom. Pour the lemon sugar butter mixture over the dough and evenly distribute fresh blueberries on top.Using your fingers, dimple the dough to incorporate the blueberries and lemon butter mixture into the surface.
Cover the pan with foil and bake at 425°F (218°C) for 15 minutes. Remove the foil and bake uncovered for an additional 20 minutes, or until golden brown and crisp on the edges.
Prepare the Glaze: While the focaccia bakes, whisk together 1 cup powdered sugar, 1 tsp almond extract (for a delicious blueberry muffin flavor!), and 1–2 tbsp lemon Juice.
Finish & Serve: Remove the focaccia from the oven, check internal temp (205°F), and let it cool for a few minutes before drizzling the glaze over the top. Slice, serve, and enjoy!