Instructions

1. Make the soup:
2. Dice 1 1/2 large white or Spanish onions (about 2 1/2 cups). Remove the germ in the middle from 3 large garlic cloves, then coarsely chop the cloves. Trim and cut 1 1/2 pounds white mushrooms into 1/4-inch thick slices.
3. Melt 1 tablespoon of the unsalted butter in a large Dutch oven or pot over medium-low heat. Add the onions and garlic, season with 1/2 teaspoon kosher salt and 1/4 teaspoon white pepper, and cook, stirring often, until softened, about 5 minutes. Add the mushrooms and the remaining 1 tablespoon unsalted butter, increase the heat to medium, and cook, continuing to stir, until the mushrooms release their liquid, 3 to 5 minutes. Increase the heat to high and cook until almost all of the liquid evaporates, 6 to 8 minutes more.
4. Add 1/3 cup dry white wine wine and let it boil until it, too, almost evaporates, about 2 minutes. Add 2 fresh parsley sprigs, 1 fresh rosemary sprig, and 6 cups chicken broth or water (with the bouillon cubes, if you’re using them), and bring to a boil. Reduce the heat, cover the pot almost completely, and cook at a gentle simmer for 20 minutes.
5. Remove the pot from the heat. If you can, remove and discard the rosemary sprig (it will have lost its leaves). Blend the soup directly in the pot with an immersion blender until very smooth. Alternatively, blend in small batches in a stand blender or food processor. If you’re using a processor or an immersion blender, you probably won’t get a super-smooth soup. If you’d like, you can strain the puréed soup through a fine-mesh strainer, but it’s really not necessary.
6. Taste and season with more kosher salt and white pepper as needed. Return the soup to the pot and heat it gently—it shouldn’t boil, it should be very hot.
7. Make the salad:
8. Trim and very thinly slice 6 medium white mushrooms. Thinly slice the white and light green parts of 2 medium scallions if desired. Pick the leaves from 3 to 4 fresh parsley sprigs and mince until you have about 1 tablespoon. Thinly slice 1/4 bunch fresh chives until you have about 1 tablespoon.
9. Divide the mushrooms, scallions, parsley, and chives among 6 soup plates; season lightly with salt and white pepper. Ladle the soup into the bowls over the salad, and top each with a dollop of crème fraiche, if desired.