Preheat the oven to 350℉
Place minced onion in a small microwave-safe bowl with 1 Tbsp water. Microwave for 2 minutes and carefully remove from microwave. Set aside.
In a 1-Qt. mixing bowl, add 1/2 cup of each cheese, softened cream cheese, taco seasoning, garlic, 2 Tbsp cilantro, 2 Tbsp enchilada sauce, and cooked onion. Add the red pepper flakes if using. Mix until well combined.
Add the chicken and gently mix. Try not to break up the chicken pieces, they lend a good texture to the enchiladas.
Pour 1/4 cup of the enchilada sauce into a shallow dish; I use a saucer. Lay your first tortilla in sauce, flip to cover both sides. Spoon filling into middle of tortilla, about 1/3 cup, and spread evenly.
Roll the tortilla up and place in baking dish, seam side down. Continue until all are made.
Add the remaining enchilada sauce, covering the enchiladas. Add remaining cheese on top. Cover baking dish tightly with foil and place in oven.
Bake for 20 minutes. Remove foil and bake for 10-15 minutes until the sauce is bubbly and the cheese is melted. Let cool for 5 minutes. Sprinkle the top with the remaining cilantro and serve.