Stuffed Mushrooms

Name: Stuffed Mushrooms
Ingredients: 1 tablespoon extra-virgin olive oil, plus more drizzling; 6 ounces sweet Italian sausage (about 2 links), removed from casings; 2 garlic cloves, minced; 1 large shallot, minced; 24 large button mushrooms, caps cleaned, stems trimmed and finely chopped; Coarse salt and freshly ground pepper; 1 tablespoon finely chopped fresh flat-leaf parsley leaves; 2 tablespoons finely chopped fresh oregano leaves, plus whole leaves for garnish (optional); 1 large egg, lightly beaten; 2 tablespoons plain dry breadcrumbs; 2 tablespoons finely grated Parmigiano-Reggiano cheese