Fillet of Sole Ponte Vecchio Style

Name: Fillet of Sole Ponte Vecchio Style
Ingredients: 4 sole fillets (8-10 ounces each) or 4 flounder fillets (8-10 ounces each); 2 cups fresh mushrooms (portobello, crimini, shiitake or white domestic); 2 tablespoons butter; 1 small onion, minced; kosher salt & freshly ground black pepper, to taste; 1 cup dry white wine; 8 plum tomatoes, cut into small dice; 1 scallion, minced; 1⁄4 cup fresh parsley, minced