Preheat oven to 425 degrees and line a baking sheet with parchment paper.
Add squash, poblano and red onion to the baking sheet. Drizzle with olive oil, oregano, paprika and a good pinch of salt & pepper. Toss to coat evenly. Place in the oven for 20 minutes, flipping halfway.
While the veggies are roasting, prepare the creamy white sauce. Melt butter in a pan over medium heat. Add flour to the pan and whisk until smooth and bubbly.
Add 1 cup of enchilada sauce and vegan chicken broth to the pan and stir to combine.
Add vegan cream cheese and green chiles and whisk until smooth. Remove from the heat and set aside. This should make about 3.5 cups of sauce
To make the filling, add the roasted veggies, black beans, diced jalapeños, corn and remaining 1/2 cup of enchilada sauce to a bowl and toss to combine. Taste the filling and add salt if needed.
Lower oven heat to 350 degrees.
To assemble, pour 1 cup of white sauce in the bottom of the baking dish, followed by 6 tortillas and 1/2 of the veggie/bean mixture. Repeat this layer, starting with 1 cup of white sauce. Finally, pour 1/2 of the remaining sauce, followed by the last 6 tortillas and then the remaining sauce.
Place the casserole in the oven, uncovered, for 20 minutes. Turn oven to broil and bake for an additional 3-5 minutes (or until top browns slightly). Remove from the oven and allow to cool for 5-10 minutes before cutting.
Top with cilantro and avocado, cut into 8 pieces and enjoy.