3 lbs / 1.3 kg yellow onions, halved and thinly sliced
¾ teaspoon salt
1½ tablespoons balsamic vinegar
1½ tablespoons Tamari
1½ tablespoons fresh thyme leaves
3 garlic cloves, minced
3 tablespoons all-purpose white flour
1 cup dry white wine
6 cups vegetable broth
freshly ground black pepper
Instructions
Heat the oil in a large pot or Dutch oven over medium heat. Add the onions, salt, and several grinds of pepper then toss to combine. Reduce the heat to low and cook for about 40 minutes, stirring every few minutes, or until the onions are very soft. Increase the heat to medium and cook 15 to 20 more minutes, stirring often, until it turns golden brown. Add the vinegar, tamari, thyme, and garlic and stir. Sprinkle the flour on the onions, stir, and cook for 2 minutes. Stir in the wine and cook 2 minutes, or until evaporated. Then add the broth and simmer over medium heat for another 30 minutes.
Preheat the oven to 450°F / 230°C and line a baking sheet with parchment paper. Place the baguette slices, topped them with cheese on the baking sheet and bake until the slices are toasted and the cheese is melted – about 8 to 10 minutes.
Ladle the soup into bowls and top each with a toasted baguette piece, fresh thyme, and if desired a pinch of red pepper flakes.
