In a medium saucepan set over medium-high heat, warm the olive oil. Shallots are added and cooked for 3 minutes or until tender. Add the mushrooms, season with salt and pepper, and simmer for about 15 minutes, or until the liquid from the mushrooms has evaporated. Cook for one minute after adding the garlic. Cook for two minutes while scraping out any browned parts after adding the Madeira wine. Add the stock and thyme, and simmer for about 30 minutes while gently stirring.
Throw away the thyme sprigs. Add the hummus to the broth and stir. Remove the filler cap from the blender to allow steam to escape, then transfer half of the soup back to the pot and boil for an additional 15 minutes. Add the lemon juice, turn off the heat, and season with salt and pepper. In a small bowl, combine the parsley, scallions, and lemon zest. Add the yogurt and lemon-parsley combination to each bowl after ladling the soup into them.