Sourdough Sheet Pan Focaccia with Caramelized Onions

Steps

1. 1

   Mix the dough

   • In a large mixing bowl, combine 150g active sourdough starter (at room temperature, around 70–75°F) and 250ml room-temperature water.
   • Stir with a wooden spoon until mostly combined, about 1 minute.
   • Add 400g bread flour and mix until all flour is hydrated and a shaggy dough forms with no dry flour visible, about 2–3 minutes.
   • The dough will feel slightly sticky.
   • Cover the bowl with plastic wrap and let rest undisturbed for 30 minutes (this is the autolyse, where flour fully hydrates and enzymes begin breaking down starches).

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   Ready when: All flour is incorporated; dough is shaggy with no dry streaks

   Tip: Water temperature is critical—use 70°F (21°C) room-temperature water to keep dough temperature around 75–78°F and ensure predictable fermentation.

2. 2

   Incorporate salt and oil

   • After the 30-minute rest, sprinkle 8g salt and 30ml olive oil over the dough.
   • Using wet fingers (damp with water), fold and pinch the dough repeatedly to incorporate the salt and oil.
   • This will take 3–4 minutes.
   • The dough will initially feel loose and shiny from the oil, then gradually come together and become cohesive.
   • There should be no visible salt grains or oil streaks remaining.

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   Ready when: Salt and oil are fully incorporated; dough is cohesive and slightly sticky, with no visible streaks

   Tip: Keep your fingers wet with cool water to prevent sticking as you fold. Adding salt and oil after the autolyse (rather than at the start) develops better gluten and ensures even distribution.

3. 3

   Bulk fermentation with stretch and folds

   • Transfer the dough to a lightly oiled container or bowl.
   • For the next 2 hours, perform a set of stretch and folds every 30 minutes (4 sets total).
   • To do a stretch and fold: wet your hand, grab one side of the dough, and stretch it up and over itself; repeat from all four sides.
   • After completing the stretch-and-fold cycles, cover the container and let the dough rest undisturbed for the remaining fermentation time.
   • The dough is ready when it has increased in volume by 50–75%, feels light and airy, and shows visible bubbles on the surface and throughout the interior.
   • It should jiggle when you move the container.
   • Total bulk fermentation typically takes 4–6 hours; we'll use 5 hours as an estimate.

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   Ready when: Dough has increased 50–75% in volume, feels puffy and light, shows visible bubbles throughout, jiggles when container moves

   Tip: Maintain dough temperature around 75–78°F (24–26°C) for consistent fermentation. If your kitchen is cool, place the bowl in a turned-off oven with the light on to create a warm proofing environment.

4. 4

   Caramelize the onions

   • While the dough ferments (start during the final 1–2 hours of bulk fermentation), slice 3–4 large yellow onions (about 1.5 kg total) into thin slices, roughly ¼ inch thick.
   • Heat 60ml olive oil in a large, heavy-bottomed skillet (10–12 inch) over medium-high heat until shimmering, about 1 minute.
   • Add the sliced onions and 5g salt, stirring to coat with oil.
   • Let them cook, stirring frequently, until they soften and release liquid, about 10–12 minutes.
   • As they soften, they'll turn translucent and reduce significantly in volume.
   • Reduce heat to medium-low and continue cooking, stirring occasionally (every 2–3 minutes), for 35–45 more minutes until the onions are deeply golden brown, completely soft, and very sweet.
   • The onions should be jammy, caramelized, with minimal liquid remaining (if there's excess liquid, continue cooking).
   • Add 5g fresh thyme sprigs if using, and season with additional salt to taste.
   • Remove from heat and let cool slightly before use.

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   Ready when: Onions are deep golden brown (not burnt), very soft, sweet, and jammy with minimal liquid in the pan

   Tip: Don't rush the caramelization by using high heat—low, slow heat over 45–50 minutes develops infinitely better flavor. Stir occasionally in the later stages to prevent scorching on the pan bottom.

5. 5

   Shape the dough in the pan

   • Lightly oil a 9×13-inch (23×33 cm) sheet pan with olive oil.
   • Once bulk fermentation is complete, gently turn the dough out onto the prepared pan (it's fine if it's slightly sticky).
   • Using lightly oiled hands or a bench scraper, gently stretch and coax the dough to fill the pan.
   • Work from the center outward toward the edges.
   • The dough doesn't need to fill the pan perfectly at this stage—it will puff during the final proof.
   • If the dough springs back too much and resists stretching, cover it and let it rest for 10–15 minutes before trying again.
   • Cover the shaped dough with plastic wrap.

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   Ready when: Dough loosely fills most of the pan and looks relaxed

   Tip: Handle gently to preserve the gas bubbles you've developed during bulk fermentation. Never punch or aggressively deflate the dough.

6. 6

   Final proof (room temperature or cold)

   • Option A (same-day): Cover with plastic wrap and let proof at room temperature (75–78°F / 24–26°C) for 2–4 hours until the dough is noticeably puffy, fills the pan completely, and springs back slowly (but not fully) when poked—there should be a slight indentation remaining.
   • Option B (overnight): Cover with plastic wrap and refrigerate for 8–12 hours.
   • When ready to bake, remove from the fridge and let come to room temperature for 30–45 minutes until it feels slightly puffy again.
   • Cold proofing develops deeper, more complex flavor.
   • For timing purposes, we'll use 3 hours for same-day proofing.

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   Ready when: Dough is noticeably puffy and fills the pan; springs back slowly when gently poked (not fully)

   Tip: For best flavor, use the cold overnight proof whenever possible. If doing same-day, keep kitchen temperature consistent by avoiding opening the oven or exposing the dough to temperature swings.

7. 7

   Preheat ovenOven 450°F / 230°C

   • About 30 minutes before baking (or as soon as final proof is complete), preheat your oven to 450°F (230°C).
   • Position an oven rack in the upper-middle position—this helps the bottom develop golden color without burning while the top bakes evenly.

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   Ready when: Oven is fully preheated (you'll see an indicator light or hear a beep)

   Tip: Use an oven thermometer if you have one—many home ovens run hotter or cooler than displayed, and 450°F is important for proper crust development.

8. 8

   Dimple, top, and final rest

   • Using damp fingertips (wet with water), gently dimple the entire surface of the dough, creating deep indentations about 1 inch apart.
   • These dimples trap oil and toppings, giving focaccia its characteristic texture and appearance.
   • Brush the surface generously with 60ml olive oil, working it into the dimples.
   • Spread the cooled caramelized onions evenly across the top, distributing them so every slice will have some topping.
   • Scatter 10g fresh rosemary leaves (roughly chopped) over the onions, then sprinkle with 5g coarse sea salt and minced garlic if using.
   • Let the topped dough rest uncovered for 15 minutes at room temperature.
   • The dough will puff noticeably during this time and feel very light.

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   Ready when: Dough is visibly puffier; tops of dimples are light and airy

   Tip: Don't press too hard when dimpling—you want to dent the surface, not deflate the entire dough. Keep fingertips damp to prevent sticking.

9. 9

   BakeOven 450°F / 230°C

   • Place the sheet pan on the upper-middle oven rack and bake at 450°F (230°C) for 25–30 minutes.
   • The focaccia is done when the top is deep golden brown and the edges are crispy and starting to curl slightly away from the pan sides.
   • The bottom should also be golden brown.
   • To verify doneness, carefully lift a corner with a spatula to peek at the bottom—it should be golden, not pale.
   • A gentle tap on the bottom crust should sound hollow.
   • If the top browns too quickly before the interior sets, you can loosely tent the pan with foil, but avoid letting the foil touch the surface.

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   Ready when: Top is deep golden brown; edges are crispy; bottom is golden; tapping the bottom sounds hollow

   Tip: Most well-ventilated ovens won't need the foil tent, but watch for excessive browning and adjust if needed.

10. 10

    Cool

    • Remove the focaccia from the oven.
    • Immediately brush or drizzle the hot surface with a little extra olive oil if desired (optional but adds richness).
    • Let cool in the pan for 10–15 minutes—this allows the crust to set and makes the bread easier to remove.
    • Transfer to a cutting board or cooling rack if you'd like to serve it warm, or let it cool completely for easier, cleaner cutting.
    • Focaccia is best served warm or at room temperature, ideally within a few hours of baking.

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    Ready when: Focaccia is cool enough to handle safely; crust is firm

    Tip: Focaccia's crust is at its crispiest when freshly baked. The longer it sits uncovered, the softer the crust becomes, which is fine for some preferences but less ideal if you want crispness.