Lasagna With Mushrooms And Lamb Sausage

Name: Lasagna With Mushrooms And Lamb Sausage
Ingredients: 1/2 pound merguez; 3 tablespoons extra-virgin olive oil, plus more for drizzling; 1 pound oyster mushrooms, stems discarded and large caps halved lengthwise; 1 pound shiitake mushrooms, stems discarded and caps thinly sliced; Salt and freshly ground pepper; 1 large red onion, thinly sliced; 2 tablespoons all-purpose flour; 3 cups mushroom stock or chicken stock; 1/4 cup dry red wine; 1/2 pound lasagna noodles, preferably flat (see Note); 4 cups fresh ricotta cheese; 1/2 pound truffled pecorino cheese, coarsely shredded (about 3 cups); 2 tablespoons unsalted butter, softened, plus more for greasing; 2 tablespoons freshly grated Parmigiano-Reggiano cheese; Parsley leaves, for garnish