# What You’ll Need:
→ Sourdough Starter
01 - 3.5 oz active sourdough starter at 100% hydration
→ Dough
02 - 14 oz bread flour
03 - 10 fl oz lukewarm water
04 - 0.35 oz fine sea salt
05 - 0.7 fl oz extra-virgin olive oil
→ Topping
06 - 2 medium yellow onions, thinly sliced
07 - 1 tablespoon olive oil
08 - 1 teaspoon flaky sea salt
09 - 1 teaspoon fresh rosemary leaves
10 - Freshly ground black pepper to taste
# Method:
01 - In a large mixing bowl, combine sourdough starter, bread flour, and lukewarm water until a shaggy dough forms. Cover and rest for 30 minutes without disturbing.
02 - Add fine sea salt and olive oil to the rested dough. Mix thoroughly until both ingredients are fully incorporated throughout the dough.
03 - Over the next 2 hours, perform 3 to 4 sets of stretch and fold motions at 30-minute intervals. Wet your hand and pull dough from the edge toward center, rotate bowl, and repeat to build gluten structure.
04 - Cover the bowl and allow dough to rise at room temperature for 6 to 8 hours until doubled in volume.
05 - Generously oil a 9x13-inch baking pan. Transfer dough carefully to pan and use oiled fingertips to gently stretch and press dough to fill the pan evenly without deflating.
06 - Cover the pan and refrigerate overnight for 8 to 12 hours. This extended rest develops superior flavor and texture.
07 - Heat 1 tablespoon olive oil in a skillet over medium-low heat. Add sliced onions and cook, stirring occasionally, for 20 to 25 minutes until golden, soft, and deeply caramelized. Transfer to a plate and cool completely.
08 - Remove focaccia dough from refrigerator and let rest at room temperature for approximately 1 hour before baking.
09 - Preheat oven to 425°F. Using your fingertips, create dimples across the dough surface. Drizzle with additional olive oil, then distribute caramelized onions evenly. Sprinkle flaky sea salt, fresh rosemary, and black pepper over the surface.
10 - Bake for 25 to 30 minutes until the crust is golden brown and edges are crisp. The focaccia should sound hollow when tapped on the bottom.
11 - Remove from oven and cool for 5 to 10 minutes before slicing. Serve warm for optimal texture and flavor.