Rinse Swiss chard leaves with cold water and dry with kitchen towel. Lay flat on a cutting board, one leaf at a time, and using sharp knife remove the membrane and cut into 2 parts lengthwise. Repeat with remaining leaves. You should end up with 12 "tortillas". Set aside.
To make enchilada sauce, in a medium bowl, combine tomato sauce, cumin, chili powder, garlic powder, salt and pepper. Whisk and set aside.
Preheat large non-stick skillet on medium heat and add 1/2 tablespoon of oil to coat. Add poblanos with a pinch of salt and pan fry for 5 minutes, stirring just a few times.
Add remaining 1/2 tablespoon oil, chicken, chili powder, cumin and salt. Cook for another 5 minutes, stirring a few times. Turn off heat, add 1/2 cup enchilada sauce and stir. Set aside.
Preheat oven to 400 degrees F. Spread a bit of enchilada sauce on the bottom of large 9" x 13" baking dish. Set aside.
To roll enchiladas, place one swiss chard leaf on a cutting board, top one end with 1/4-1/3 cup chicken mixture (depending on its size) and roll tightly. Place into previously prepared baking dish and repeat this step with remaining enchiladas. You should end up with 12 rolls. Spread any remaining chicken mixture on top.
Top enchiladas evenly with remaining enchilada sauce and sprinkle with cheese. Bake for 10 minutes, remove from the oven, cover with foil and let stand for 5 minutes.
Serve warm with avocado, cilantro and lime, if desired.
Notes
Store: Refrigerate leftovers covered for up to 2 - 3 days. I don't recommend to freeze this dish as greens will become soggy.
Poblanos replacement: Poblanos are mild green chili peppers that are sold in many supermarkets. If you can't find poblanos, substitute with 2 green bell peppers and 2 seeded jalapeños. This substitute will give you similar flavor, sweetness and spiciness as poblanos.