Caramelize the Onions: This is the most important step! In a large Dutch oven or heavy-bottomed pot, melt the vegan butter over medium-low heat. Add the thinly sliced onions and a pinch of salt. Cook, stirring occasionally, for 30-40 minutes. Be patient! You want them to become a deep, golden-brown color, not just soft. This is where the flavor is built.

Add Garlic and Deglaze: Once the onions are beautifully caramelized, add the minced garlic and cook for one more minute until fragrant. Pour in the white wine to deglaze the pot, scraping up all the browned bits from the bottom. Let it simmer for 2-3 minutes until the wine has mostly evaporated.

Simmer the Soup: Add the vegetable broth, tamari, and thyme leaves to the pot. Bring to a boil, then reduce the heat and let it simmer for at least 20 minutes to allow the flavors to meld. Season to taste with salt and plenty of black pepper.

Prepare the Topping: While the soup simmers, preheat your oven’s broiler. Place oven-safe soup bowls on a baking sheet. Ladle the hot soup into the bowls.

Top and Broil: Place a slice of toasted baguette on top of the soup in each bowl. Generously pile the vegan cheese on top of the bread.

Melt and Brown: Carefully place the baking sheet under the broiler for 2-4 minutes, watching closely, until the vegan cheese is melted, bubbly, and has some golden-brown spots.

Serve Carefully: Remove from the oven (the bowls will be very hot!) and let them cool for a few minutes before serving.