Coarsely chopped and well-seasoned mushrooms and cashews make the perfect vegetarian ground meat substitute in this hearty and savory casserole. To cut down on time, use your favorite store-bought salsa. You can even assemble the dish in advance then bake it just before serving, for an easy weeknight dinner. Like the mushroom “meat” filling? Double that part of the recipe and freeze it to use for other easy vegetarian dishes like tacos, sloppy joes or pasta!
Preheat the oven to 350 degrees F. Grease a 9-inch square or 9-by-13-inch baking pan with vegetable oil or cooking spray.
Combine the mushrooms and cashews in a food processor and pulse until coarsely chopped.
Heat the olive oil in a large deep skillet over medium heat. Add the chopped mushrooms and cashews and season with 1/2 teaspoon salt. Cook, stirring occasionally, until the mushrooms cook down and reduce, about 5 minutes.
While the mushrooms cook, combine the onion and garlic in the food processor bowl (no need to rinse it out first) and pulse until coarsely chopped. Transfer to the skillet with the mushrooms. Add all of the spices and tomato paste and stir to combine. Continue to cook until the liquid has evaporated and the mixture has thickened and reduced, 5 to 10 minutes. Add the spinach and cook 3 minutes. Remove from the heat and stir in 1 cup of the sour cream and 1 cup of the mozzarella. Set aside.
Place about 1/2 cup of the salsa verde in the baking pan and spread to coat the bottom in a thin layer. Working with 1 tortilla at a time, place a generous spoonful of the filling down the center of the tortilla. Roll it closed and place seam-side down in the baking pan. Repeat with the remaining tortillas and filling, using as much filling as possible in each tortilla. (If using a square pan, you may need to cut one of the tortillas in half to fill the space.)
Pour the remaining salsa verde over the filled baking pan, tilting to spread the salsa evenly. Sprinkle the top with the remaining 1/2 cup mozzarella.
Bake until bubbling, the cheese is melted and slightly golden and the tortilla edges are toasted, about 30 minutes.
Let cool in the pan for 15 minutes, then serve topped with dollops of the remaining sour cream and sprinkled with the cilantro.