Preheat oven to 400 degrees F. Place tortillas directly on the oven rack in a single layer, baking until toasted and crisp, about 5 minutes; let cool 5-10 minutes before breaking into pieces.
Heat olive oil in a large cast iron skillet over medium heat. Add onion and poblano, and cook, stirring frequently, until tender, about 3-4 minutes. Stir in garlic and cumin until fragrant, about 1 minute.
Stir in diced tomatoes, enchilada sauce and chicken; season with salt and pepper, to taste.
Bring to a boil; reduce heat and simmer, stirring occasionally, until flavors have blended, about 5 minutes.
Stir in tortillas until evenly combined; sprinkle with cheeses.
Place into oven and bake until bubbly and cheeses have melted, about 15-20 minutes.
Serve immediately with desired toppings.
Notes
Toast the tortillas. Crisping the tortillas beforehand is a key step, creating a barrier and preventing them from becoming soggy.
Use red or green enchilada sauce. Use your favorite brand of enchilada sauce, mild or spicy. Homemade enchilada sauce is even better.
Mix it up. Swap out the chicken for crumbled ground beef (or turkey) seasoned with taco seasoning or make it vegetarian by skipping the chicken and adding in black beans + bell pepper + broccoli (or cauliflower) + leafy greens.
Make it gluten-free. This recipe can easily be made GF by swapping out the tortillas for gluten-free tortillas.