French Onion Soup Focaccia

All the soul of a bowl of French onion soup pressed into a slab of pillowy focaccia — deeply caramelized onions (cooked until they nearly collapse into themselves), a slick of beef-enriched pan drippings worked into the dough, and a blanket of melted Gruyère blistered under the broiler. This recipe is scaled for an 8×8-inch pan, making a smaller but equally indulgent batch. It's a weekend project that rewards patience at the stove.

Ingredients

• unsalted butter – 1½ tablespoons
• yellow onions, thinly sliced into half-rings – about 3 cups raw
• kosher salt – ½ teaspoon
• dry sherry or dry white wine – 1½ tablespoons
• fresh thyme leaves – ½ teaspoon
• black pepper, freshly ground – ⅛ teaspoon

• warm water (100–110°F / 38–43°C) – ¾ cup + 2 tablespoons
• active dry yeast – 1¼ teaspoons
• granulated sugar – ½ teaspoon
• all-purpose flour – 2 cups + 2 tablespoons
• kosher salt – ¾ teaspoon
• extra-virgin olive oil, divided – 3 tablespoons total

• beef broth – 1 tablespoon
• Gruyère cheese, coarsely grated – 1 cup loosely packed
• flaky sea salt – ¼ teaspoon

Instructions

1. Caramelize the onions: Melt the butter in a wide, heavy skillet over medium heat. Add the sliced onions and kosher salt, stirring to coat. Cook, stirring every few minutes, for 45–55 minutes total, adjusting heat to medium-low if they're browning too fast in spots. You want them to go from translucent to golden to deep amber — they should look almost jammy and reduced to about one-quarter of their original volume. This is the step you cannot rush; under-caramelized onions will taste raw and sweet rather than rich and savory. When they're deeply colored and very tender, add the sherry and scrape up any browned bits from the bottom of the pan. Stir in the thyme and black pepper, cook 1 more minute, then remove from heat and let cool.
2. Make the dough: Combine ¾ cup + 2 tablespoons (210g) warm water, 1¼ teaspoons (4g) active dry yeast, and ½ teaspoon (2g) granulated sugar in the bowl of a stand mixer. Stir briefly and let sit for 5–8 minutes until foamy, which tells you the yeast is active. Add 2 cups + 2 tablespoons (250g) all-purpose flour, ¾ teaspoon (3g) kosher salt, and 1½ tablespoons (20g) of the olive oil. Mix on low speed with the dough hook until combined, then increase to medium and knead for 6–7 minutes, until the dough is smooth, slightly tacky, and pulls cleanly away from the sides of the bowl.
3. First rise: Pour ½ tablespoon (7g) of olive oil into a large bowl and turn the dough to coat. Cover tightly with plastic wrap and let rise at room temperature for 1 to 1½ hours, until roughly doubled in size.
4. Pan and second rise: Pour the remaining 1 tablespoon (14g) of olive oil into an 8×8-inch baking pan and spread it to coat the bottom. Turn the risen dough out into the pan and gently press and stretch it toward the edges — it will spring back, so let it rest 5 minutes and stretch again. It doesn't need to reach every corner perfectly. Drizzle the 1 tablespoon (15g) of beef broth evenly over the surface of the dough (this adds that savory, soup-like depth). Scatter the cooled caramelized onions evenly over the top, pressing them gently into the dough. Cover loosely with oiled plastic wrap and let proof for 45 minutes to 1 hour, until noticeably puffed.
5. Dimple and bake: Preheat your oven to 425°F / 220°C (convection: 400°F / 200°C). With well-oiled fingertips, press deep dimples all across the surface of the dough, pushing almost all the way down to the pan — this gives focaccia its signature texture and helps the toppings settle in. Scatter the 1 cup (100g) Gruyère evenly over the top. Bake for 20–24 minutes, until the cheese is melted, the edges are deeply golden, and the underside is crisp when you peek with a spatula. The smaller pan may finish on the earlier end of the range, so start checking at 20 minutes.
6. Finish and serve: As soon as the focaccia comes out of the oven, scatter the ¼ teaspoon (0.75g) flaky sea salt over the top. Let it cool in the pan for at least 10 minutes before cutting — this lets the cheese set slightly and makes cleaner slices. Cut into squares (about 9 squares from a 3×3 grid) and serve warm. It's excellent on its own, or alongside a bowl of clear broth.