Heat oil and butter in a large skillet over medium-high heat. Saute onion, chile, garlic, and 1/4 teaspoon salt until onions are translucent, 2 to 4 minutes. Add mushrooms and cook, stirring, over high heat, until mushrooms turn deep golden brown and release their liquid, 4 to 6 minutes. Remove from heat and sprinkle with oregano. Adjust salt if necessary.Advertisement
Toast tortillas over the flame of a gas burner, turning with tongs, until crisp and blackened in spots. (You can also char them in the broiler.) Divide mushroom mixture among tortillas and sprinkle with Parmesan.
This recipe is adapted with permission from "Super Natural Every Day: Well-Loved Recipes from My Natural Foods Kitchen" by Heidi Swanson, copyright 2011. Published by Ten Speed Press, a division of Random House, Inc.