In a medium saucepan, add olive oil and heat over medium heat. Once hot, add the garlic and saute for 30 seconds. Add the chipotle chilis, then stir and break them into smaller pieces. Cook for 1 minute.

Stir in the chicken stock, crushed tomatoes, salt, cumin, black pepper, chili powder, and chipotle chili powder (if using). Bring the sauce to a boil over medium-high heat, then reduce to a simmer. Cook until thickened, about 5 minutes.

Transfer to a blender or food processor and puree on medium speed until smooth, about 30 seconds—season with salt and pepper to taste. Adjust with chicken broth if needed to thin the consistency.

Adjust the oven rack to the center position—Preheat to 400ºF (204ºC).

Place the chicken between two plastic sheets or in a large plastic bag. Use a meat mallet to flatten to an even thickness, about ½-inch thick. Repeat with the remaining pieces. Alternatively, cut in half horizontally for pieces 1-inch thick or larger to make cutlets.

In a small bowl, combine salt, 1 teaspoon of cumin, paprika, garlic powder, and black pepper. Reserve 1 teaspoon of the mixture. Evenly season each side of chicken with the mixture.

Heat a saute pan over medium heat. Add olive oil. Once hot and shimmering, add the chicken. Cook until lightly golden brown, about for 5 to 7 minutes. Flip and cook until no longer pink and the internal temperature reaches 160 to 165ºF (71 to 74ºC) on a meat thermometer, about 5 to 7 minutes. Transfer to a plate to cool.

Use your fingers or two forks to shred the chicken into smaller pieces. Alternatively, chop them with a knife. Add the reserved seasoning mix and combine until evenly coated.

Place the tortillas in a pan over medium-high heat to lightly toast and make them pliable. Alternatively, warm them directly over a gas flame for 10 to 15 seconds on each side.

Lightly coat a 13x9 baking dish with cooking spray or oil. Evenly spread ½ cup of the enchilada sauce on the bottom. Pour ½ cup of enchilada sauce into a shallow bowl large enough to fit the tortillas. Lightly dip each side of the tortilla in the sauce. Transfer to a plate and fill the center with about ⅓ cup of chicken. Roll into a cylinder and transfer to the baking dish. Repeat the process until 10 enchiladas are rolled and lined up. Evenly spread the remaining sauce over the top then sprinkle with Monterey jack cheese and cheddar.

Cover the baking dish with foil and bake until the cheese is melted and bubbly, 15 to 20 minutes.

Garnish with green onions and cilantro. Serve while still hot.