Optional:
Preheat the oven to gas mark 5. Coat a 9x13-inch baking dish with cooking spray.
Heat 4 tbsp olive oil over medium heat in a large sauté pan. Add the mushrooms, season with ½ teaspoon of salt and a pinch of ground pepper. Cook, stirring occasionally, until the mushrooms are soft and most of the moisture has evaporated, about 15m.
Pour in the remaining 2 tbsp of olive oil and stir in the kale and tin of black beans if using. Season with 1 tbsp cumin, ½ tsp of salt, and a pinch of ground pepper. Cook until the kale is wilted and soft, 3-5m.
To assemble the casserole, arrange 5 of the tortillas in a single layer in the bottom of the baking dish. Spread ⅔ cup of the salsa over the tortillas, sprinkle over 2 tbsp nutritional yeast if using, then top with half of the kale and mushroom mixture. Top with another layer of 5 tortillas, then spread with another ⅔ cup of the salsa and 2 tbsp nutritional yeast, and top with the remaining kale and mushrooms. Top with the last 5 tortillas and spread the remaining salsa across the top of the tortillas. Sprinkle 2 tbsp nutritional yeast and a handful of chopped coriander over the top.
Cover the baking dish with foil and bake for 20 minutes, until heated through. Remove from the oven. Let the casserole sit for a few minutes before serving with toppings, if using.
From The Kitchn