SERVES 6
2 pounds mushrooms (see Note above), cleaned and sliced
¼ inch thick (about 3 quarts)
4 tablespoons unsalted butter
1 large leek, white and pale green parts only, split in half
and cut into ¼-inch-thick half-moons (about 1 cup)
1 medium onion, finely sliced (about 1 cup)
2 teaspoons fresh thyme leaves
3 tablespoons all-purpose flour
1 cup milk
4 cups homemade or low-sodium canned chicken stock,
plus more if necessary
2 bay leaves