1-First Steps: Getting Started: Begin by heating 6 tablespoons of oil in a large pot or Dutch oven over medium heat. Add the 3 pounds of thinly sliced medium yellow onions, ¾ teaspoon salt, and a dash of pepper, then toss everything together to coat. Reduce the heat to low and cook for about 40 minutes, stirring every few minutes until the onions become very soft.

2-Caramelizing and Building Flavor: Once the onions are soft, increase the heat to medium and cook for another 15 to 20 minutes until they turn a golden brown color. This step is crucial for that deep, sweet flavor from the caramelized onions. Stir in 1½ tablespoons balsamic vinegar, 1½ tablespoons tamari, 1½ tablespoons fresh thyme leaves, and 3 cloves of minced garlic, mixing well to blend the flavors.

3-Caramelizing and Building Flavor: Sprinkle 3 tablespoons of all-purpose white flour over the onions and stir, cooking for 2 minutes to eliminate any raw taste. Pour in 1 cup of dry white wine and cook until it’s mostly evaporated, about 2 minutes. Finally, add 6 cups of vegetable broth and let the soup simmer uncovered over medium heat for 30 minutes, allowing all the tastes to meld together.

4-Finishing Touches: Preheat your oven to 450°F and line a baking sheet with parchment paper. Place baguette slices topped with Gruyère cheese, aged cheddar, and/or Parmesan cheese on the sheet, and bake for 8 to 10 minutes until the bread is toasted and the cheese melts beautifully. Ladle the hot soup into bowls, top each with a cheesy baguette slice, fresh thyme, and a pinch of red pepper flakes if you like a bit of heat. Serve immediately for the best experience.