Layered Tortilla Lasagna

Name: Layered Tortilla Lasagna
Ingredients: About 4 tablespoons vegetable oil; 3 cups (about 6 ounces) sliced stemmed mushrooms; 1 1/2 cups corn kernels, preferably fresh and cut off the cobs (about 2 ears); 8 cups (about 10 ounces) packed, stemmed spinach leaves, well rinsed but not dried; 1/2 teaspoon salt; 16 tortillas (this is better with store-bought rather than homemade); 5 cups Chipotle Cascabel Salsa or substitute; 1 cup heavy (whipping) cream, creme fraiche or plain yogurt; 3 cups (12 ounces) shredded Mexican asadero-style cheese, brick, Monterey Jack or just about any melting cheese you like; 15- or 16-ounce carton ricotta cheese; About 1/3 cup chopped fresh cilantro, for garnish