Heat a large soup pot on high with 1 tablespoon of water. When the water begins to sputter, add the onion, celery, and carrot, and cook for 7 to 8 minutes, stirring frequently as the edges of the onion browns slightly, and adding a little water as needed to prevent sticking.Stir in the mushrooms and garlic, and continue to cook while stirring for an additional 5 minutes, adding water as needed.Add the 5 cups of water, potatoes, tomato paste, dried Italian herbs, and paprika. Bring to a boil, and then reduce heat to a low boil. Stir in the rosemary and cook covered for 15 minutes, stirring occasionally. Add the peas, and cook for 5 minutes more, or until the carrots and potatoes are tender.Place 2 cups of the stew (broth and vegetables) into a blender, and blend under very smooth. Stir this back into the pot to thicken the stew, and stir in the parsley. Serve with a few twists of ground black pepper and, if you like, add a small sprig of rosemary as garnish.