1. In small bowl, mix all slaw ingredients; set aside.
2. Heat taco shells as directed on box.
3. Meanwhile, in large skillet, heat oil over medium-high heat. Cook mushrooms in oil 3 to 5 minutes, stirring occasionally, until they begin to brown. Add onion; cook 2 to 3 minutes longer. Stir in chili powder and grill seasoning.
4. To serve, spoon mushroom mixture into warmed taco shells; top with avocado slices and spicy cabbage slaw.
1. This same slaw is perfect on our Sweet-and-Sour Portabella Sliders, so you can keep those ingredients on hand to make a different recipe another night.
2. Replace the spicy cabbage slaw with finely shredded iceberg lettuce, diced tomato and sour cream for a mild taco, perfect for kids.
3. Make chicken-mushroom tacos by adding 1/2 to 1 cup of diced or shredded cooked chicken. Add after the onion and heat until mixture is hot.