Harissa Portobello Mushroom "Tacos"

Name: Harissa Portobello Mushroom "Tacos"
Prep time: 20 min
Cook time: 10 min
Total time: 30 min
Cuisine: Latin American, Mexican, American
Ingredients: 1 pound (450g) portobello mushrooms; 1/4 cup (60g) spicy harissa, or use a mild harissa; 3 tablespoons olive oil (divided); 1 teaspoon ground cumin; 1 teaspoon onion powder; 6 collard green leaves; 2 medium ripe avocados; 2 tablespoons chopped tomatoes; 2 tablespoons chopped red onion; 1 1/2 to 2 tablespoons lemon or lime juice; pinch of salt; 1 tablespoon chopped cilantro; cashew cream; chopped tomatoes; chopped cilantro