
6 tablespoons salted butter
6 large sweet onions, thinly sliced
1 tablespoon packed dark brown sugar
2 cloves garlic, minced
2 tablespoons all-purpose flour
4 cups beef stock
½ cup dry red wine
1 tablespoon Worcestershire sauce
4 to 6 sprigs fresh thyme, plus additional for garnish
2 bay leaves
1 teaspoon coarse kosher salt
1 teaspoon coarse-ground black pepper
32 (¼-inch-thick) slices baguette
3 cups shredded white cheese blend (Fontina, Gouda, Gruyère and Parmesan)