Sausage and Mixed Mushroom Lasagna

Name: Sausage and Mixed Mushroom Lasagna
Ingredients: 1 teaspoon dried oregano; 2 tablespoons extra-virgin olive oil; 2 cloves garlic, thinly sliced; One 28-ounce can whole plum tomatoes, lightly crushed; Kosher salt and freshly ground pepper; Two 4-ounce packages mixed mushrooms, coarsely chopped; 1 pound sweet Italian sausage, removed from casings; 1 pound mozzarella cheese; Two 15-ounce containers ricotta cheese; 1 large egg; 3 fresh lasagna sheets (about 7 ounces); 2 tablespoons chopped fresh parsley; Serving suggestions: Green salad and garlic bread