# Components:
→ 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 - 0.68 fl oz extra-virgin olive oil
→ Topping
06 - 2 medium yellow onions, thinly sliced
07 - 1 tbsp olive oil
08 - 1 tsp flaky sea salt
09 - 1 tsp fresh rosemary leaves
10 - Freshly ground black pepper to taste
# Directions:
01 - In a large bowl, combine the sourdough starter, bread flour, and lukewarm water until a shaggy dough forms. Cover and let rest for 30 minutes.
02 - Add fine sea salt and extra-virgin olive oil to the dough. Mix thoroughly until fully incorporated.
03 - Over the next 2 hours, perform 3 to 4 sets of stretch and folds at 30-minute intervals to develop gluten strength.
04 - Cover the bowl and allow the dough to rise at room temperature for 6 to 8 hours until doubled in volume.
05 - Oil a 9x13-inch baking pan generously. Gently transfer the dough to the pan and carefully stretch it to fill the entire surface using oiled fingers. Cover the pan.
06 - Refrigerate the covered pan overnight or for 8 to 12 hours to develop flavor and improve texture.
07 - While the dough rests, heat 1 tbsp olive oil in a skillet over medium-low heat. Add the sliced onions and cook, stirring occasionally, for 20 to 25 minutes until deeply golden, tender, and sweet. Transfer to a plate and cool completely.
08 - Remove the dough from the refrigerator and let it rest at room temperature for approximately 1 hour.
09 - Preheat the oven to 425°F. Create dimples across the dough surface using your fingertips. Drizzle with additional olive oil and distribute the caramelized onions evenly across the top. Season with sea salt, rosemary, and freshly ground black pepper.
10 - Bake for 25 to 30 minutes until the surface is golden brown and the edges are crisp.
11 - Allow the focaccia to cool for several minutes before slicing and serving.
