For the soup
4 tablespoons unsalted butter
10 cups thinly-sliced green cabbage (from 1 medium-large head)
1 medium onion, thinly sliced
8 cloves garlic, coarsely chopped
2 tablespoons fresh thyme leaves, plus more for garnish
8 cups vegetable broth
1 tablespoon low-sodium soya sauce
1 teaspoon course salt, or more as needed
1 teaspoon freshly-ground black pepper
For the toasts
Half long, stale baguette, cut into ¼-inch slices (about 32 slices)
½ cup grated Parmiggiano-Reggiano cheese or Gruyère
For the soup: Melt the butter over medium heat in a large pot or Dutch oven.
Once the foam subsides, add the cabbage, onion and garlic; cook, stirring often, until the cabbage wilts, about 10 minutes.
Reduce the heat to medium-low, cover and cook for 35 to 45 minutes, stirring occasionally, until the cabbage is tender and has reduced (wilted) by at least half.
Uncover; stir in the 2 tablespoons of thyme and cook, stirring often, until the liquid evaporates and the cabbage starts to lightly brown, 6 to 8 minutes.
Stir in the broth. Increase the heat to medium-high and bring to a boil.
Use a wooden spoon or spatula to scrape any brown bits off the bottom of the pot and incorporate them into the broth.
Reduce the heat to medium-low, cover and cook for 10 minutes so the flavours meld. Stir in the tamari, salt and pepper.
Taste, and add more salt, as needed.
While the soup is cooking, make the toasts: position an oven rack 4 to 6 inches from the broiling element; preheat the broiler.
Arrange the baguette slices on a baking sheet. Sprinkle generously with the cheese.
Broil until the cheese melts, 1 to 2 minutes, and the bread has crisped and browned on the edges.
Serve the soup hot, in big bowls, with a few toasts floating in each one. Scatter fresh thyme leaves in each.