French Onion Gruyère Focaccia Bread

1 Add the warm water, instant yeast and honey to the bowl of a stand mixer. Let stand for about 5 minutes, until the yeast begins to look foamy.
2 Add the bread flour, 2 teaspoons kosher salt and 2 tablespoons olive oil. Attach the dough hook and mix on low until a shaggy dough forms.
3 Increase to Speed 2 and knead for 6–8 minutes. The dough should look smoother and stretchy, pulling from the sides of the bowl while remaining soft and a little sticky at the bottom.
4 With lightly oiled hands or a scraper, transfer the dough to a lightly oiled bowl. Cover and let rise in a warm place for 60–90 minutes, until roughly doubled.
5 Meanwhile, make the topping. Melt the butter with 1 tablespoon olive oil in a large skillet over medium-low heat. Add the onions, ½ teaspoon kosher salt and pepper. Cook for 25–35 minutes, stirring occasionally, until soft and deeply golden. Stir in the thyme and let cool.
6 Pour about 2 tablespoons olive oil into a 9-by-13-inch metal baking pan and spread it across the bottom and sides. Transfer the risen dough to the pan and gently stretch it toward the corners. If it springs back, let it rest for 10 minutes and stretch it again.
7 Cover and let rise for another 30–45 minutes, until visibly puffy. Meanwhile, preheat the oven to 425°F.
8 Drizzle the dough with a little more olive oil. With oiled fingertips, press deep dimples across the surface. Distribute the cooled onions and shredded Gruyère over the dough. Add a little more thyme and a pinch of flaky salt.
9 Bake for 22–27 minutes, until the edges are golden brown and the center is baked through. If the cheese browns too quickly, loosely tent the bread with foil for the last few minutes.
10 Let rest in the pan for 10 minutes. Lift out, cut into 12 rectangles and serve warm.
Recipe Notes
12 The dough should be sticky. Use oiled hands to handle it instead of adding a lot of extra flour.
13 A metal pan helps the bottom and edges brown well.
14 Caramelize the onions during the first rise to make the most of the waiting time.
15 Freshly shredding the Gruyère helps it melt evenly.