01 -
2 tablespoons unsalted butter, melted.
02 -
3 pounds yellow onions, thinly sliced (6 medium onions).
03 -
4 garlic cloves, minced.
04 -
1 tablespoon fresh thyme leaves or 1 teaspoon dried thyme.
05 -
1½ teaspoons kosher salt, plus more to taste.
06 -
¼ teaspoon ground black pepper.
07 -
4 cups low-sodium beef broth.
08 -
½ cup dry white wine (Sauvignon Blanc).
09 -
8-12 slices French bread, ¼-inch thick.
10 -
3 tablespoons olive oil.
11 -
½ cup shredded Gruyere cheese.