In a large skillet, heat 1 tablespoon of vegetable oil over medium heat. Add the crushed fire-roasted tomatoes, chicken broth, chipotle peppers, cumin, salt, and black pepper. Stir well to combine and let the mixture simmer for about 10 minutes, allowing the flavors to meld together.
In a mixing bowl, combine the shredded rotisserie chicken, sour cream, sliced green onions, and 1 cup of the shredded Mexican cheese blend. Mix until everything is well combined and coated in the sour cream.
Preheat your oven to 375°F (190°C). In the prepared baking dish, spread a thin layer of the sauce on the bottom. Take a corn tortilla, fill it with a generous scoop of the chicken mixture, and roll it up tightly. Place the rolled tortilla seam-side down in the baking dish. Repeat with the remaining tortillas.
Once all the enchiladas are in the dish, pour the remaining sauce over the top, ensuring each enchilada is well coated. Sprinkle the remaining 1 cup of shredded Mexican cheese blend evenly over the sauce.
Drizzle the remaining 1 tablespoon of vegetable oil over the top of the enchiladas. Cover the dish with aluminum foil and bake in the preheated oven for 20 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and slightly golden.
Once baked, remove the enchiladas from the oven and let them cool slightly. Serve warm, topped with fresh cilantro, avocado, and additional sour cream and green onions, if desired.