Mushroom and Leek Soup with Parsley Dumplings

Bring 2 cups water and porcini mushrooms to boil in small saucepan. Remove from heat, cover, and soak 20 minutes. Using slotted spoon, transfer mushrooms to work surface; slice thinly. Reserve cooking liquid. Heat 2 tablespoons oil in heavy large skillet over medium-high heat. Add garlic; stir 30 seconds. Add crimini mushrooms and thyme; sprinkle with sea salt and sauté until mushrooms are browned, stirring often, about 12 minutes. Add Sherry; stir until liquid is absorbed, about 1 minute. Set mushroom mixture aside. Heat 1 1/2 tablespoons oil in another heavy large skillet over medium-high heat. Add onion; cook until translucent and beginning to brown, stirring often, about 6 minutes. Add leeks; reduce heat to medium, sprinkle with sea salt, and sauté until vegetables are soft and golden, stirring often, about 15 minutes. Bring broth to simmer in large pot over medium-high heat. Pour in reserved mushroom cooking liquid, leaving sediment behind. Add all mushrooms, onion mixture, and cayenne. Simmer 1 minute to heat through. Season to taste with salt. DO AHEAD: Can be made 1 day ahead. Cool, cover, and chill.