1. To make Soup: Heat oil in pot over medium-high heat. Add mushrooms and onion, and sauté 5 minutes. Stir in Italian seasoning, then broth. Cover, and bring to a boil. Set aside 1/2 cup broth, then add noodles; simmer 3 minutes, stirring occasionally. Add green beans, and simmer 3 minutes. Remove from heat.
2. Whisk reserved 1/2 cup broth into mascarpone in bowl. Slowly stir mascarpone mixture into Soup.
3. To make Gremolata: pulse parsley, garlic, and lemon zest in food processor until finely chopped.
4. Ladle Soup into bowls. Garnish each with 2 tsp. Gremolata.