Prepare chicken by boiling or baking until fully cooked, then shred it.
Heat vegetable oil in a skillet over medium heat and sauté chopped onion and minced garlic until soft, about 3-4 minutes.
Add shredded chicken to the skillet with onions and garlic. Season with cumin, chili powder, salt, and pepper. Cook for another 3-5 minutes.
Pour a small amount of enchilada sauce into the bottom of a baking dish to prevent sticking.
Place a spoonful of chicken mixture in the center of each flour tortilla. Sprinkle with shredded cheese, roll tightly, and place seam side down in the baking dish.
Pour remaining enchilada sauce over rolled tortillas and sprinkle remaining cheese on top.
Cover dish with foil and bake at 375°F (190°C) for 20-25 minutes. Remove foil and bake an additional 5-10 minutes until cheese is bubbly and golden.
Let enchiladas rest a few minutes before serving. Garnish with chopped cilantro and serve with sour cream.