In a large saucepan, heat the olive oil over moderate heat. Add the onion and garlic and cook, stirring occasionally, until soft, about 5 minutes. Deglaze with the white wine. Stir in the diced tomatoes, tomato paste, mushrooms and dried herbs and bring to a simmer. Add the mussels.
Cover and simmer for 10 minutes. Stir in the olives and fresh tomatoes. Cover and simmer for 5 more minutes. Discard any mussels that do not open. Serve with Pomme Frites!
This recipe and photo are courtesy of Savor in San Antonio.