French Onion Soup Focaccia

For the focaccia: In a large bowl, pour in the lukewarm water, then sprinkle the yeast and sugar over the top. Gently mix with a dough whisk or wooden spoon and let sit until the yeast has bloomed, about 10 minutes. The surface should appear foamy.

Stir in the olive oil and salt. Add the all-purpose flour and bread flour, mixing with the dough whisk or wooden spoon until no dry flour streaks remain.

Cover the bowl and let the dough rise for 45 minutes. After 45 minutes, lightly wet your hands. Perform a stretch and fold by gently pulling the top edge of the dough up and over the dough ball. Repeat this process until you have worked your way around the entire dough. Cover the bowl again and let it sit in a warm spot.

After 30 minutes, repeat the stretch and fold process. Cover the bowl and perform two more sets of stretches and folds, each 30 minutes apart. After the 4th stretch and fold, cover the bowl and let sit for 30 minutes.

At this point, the dough should have doubled in volume and feel smooth to the touch. The dough is now ready for use or can be chilled overnight.

For the toppings: Lightly oil a 9x13-inch metal cake pan. Gently stretch the focaccia base into the pan, ensuring it reaches all four corners. Cover the focaccia and let it rise for about 1 hour.

Meanwhile, melt the butter in a light-colored skillet over medium heat. Add the sliced onions and a generous pinch of salt, cooking over medium-low heat, stirring often, until the onions are deeply caramelized, about 40 minutes. You may need to add water, 1/4 cup at a time, to prevent burning. After 40 minutes, the onions should be deeply browned and have a jammy consistency. Remove from heat and let cool slightly.

Preheat the oven to 450 degrees F (230 degrees C).

Lightly drizzle the surface of the focaccia with olive oil. Use your fingers to create dimples across the surface, then scatter the Gruyère cheese in an even layer. Dimple the surface again, then dollop the caramelized onions all over. Sprinkle with Herbes de Provence.

Bake in the preheated oven until the focaccia and cheese are golden brown and bubbly, approximately 25 to 30 minutes.

Remove from the oven and let sit in the pan for about 10 minutes, then carefully slide the focaccia onto a cutting board. Let cool for an additional 10 minutes before slicing and serving.