Preheat the oven to 350°F. Spray a 9x13 inch baking dish with nonstick cooking spray.
Heat the tablespoon of olive oil in a large nonstick skillet over medium high heat. Add the butternut squash cubes, and stir until golden and fork-tender, about 10 minutes. Add the additional ½ tablespoon of oil along with the spinach, cumin and chili pepper, and stir until wilted. Take off the heat and mix in the chicken and corn and season with a pinch each of salt and pepper. Transfer to a bowl and set aside.
Meanwhile, in the same nonstick skillet (wiped out), heat the olive oil over medium heat. Add the garlic and stir until fragrant, about 30 seconds. Add in the tomato sauce, chipotle, adobo sauce, maple syrup and cumin. Let simmer for about 5 minutes, stirring often. Season with salt and pepper to taste.
Add about 1/3 cup of the sauce to the chicken mixture and 1 cup of the shredded cheese.
Spread about ½ cup of the tomato sauce on the bottom of the dish. Assemble the corn tortillas with about ½ cup of the filling, roll each tortilla and place seam side down into the baking dish.
Pour the remaining tomato sauce over the enchiladas, and sprinkle with the remaining cheese. Cover the casserole and bake for 20 minutes. Uncover and bake for 5 – 10 more minutes, or until the cheese is bubbling and golden brown.
Serve with fresh cilantro, avocado slices, and lime wedges.