Preheat oven to 425°F (218°C). Rub butternut squash and mushrooms with 1 Tbsp. oil and sprinkle with 1/2 tsp. salt. Roast squash and mushrooms 20 minutes. Pull pan from oven and remove mushroom and set aside. Stir squash and roast 15 minutes longer or until squash are browned and fully cooked.
While squash and mushrooms are roasting, heat remaining tablespoon oil in large pan. Add onion and sauté for several minutes. Add garlic and jalapeño and sauté several more minutes until both start to brown.
Add black beans, cilantro, cumin, chili powder, lime juice, remaining salt, roasted squash and mushrooms. Stir over medium heat for 2-3 minutes. Turn oven temperature down to 375 degrees F.
Ladle a thin layer of enchilada sauce into an 11x7" casserole dish.
Microwave tortillas on high heat for 30 seconds to soften (you may want to only microwave 3 tortillas at a time so that they stay warm and don't break while preparing them).
Spoon 1 - 1.5 cups of veggie mixture into each tortilla along with 1 Tbsp. of cheese and fold bottom side lengthwise to seal. Place sealed side down into casserole dish.
Ladle remaining sauce over enchiladas and top with cheese. Bake for 15 - 20 minutes or until cheese is melted. Garnish with remaining cilantro. Other possible toppings include green onion, cotija cheese, tomato, and avocado. Enjoy!