Preheat oven to 400℉ ( 205℃). Melt butter in a skillet over medium heat. Add onion and garlic. Sauté for 4-5 minutes to soften.
1 large White onion, chopped, 4 cloves Garlic, minced, 1 tbsp Butter
In a large bowl mix together the chopped chicken, sour cream, salsa verde, chopped chiles, cilantro, and cumin. Mix in the sautéed onions and garlic to combine. Tear tortillas into rough pieces.
5 cups Leftover or rotisserie chicken, chopped, 2 cups Sour cream, 16 oz Jarred salsa verde, 14 oz Canned diced chiles, ½ cup Fresh cilantro, chopped, 2 tsp Cumin, 20 small White corn tortillas
Spoon ¼ of the chicken filling over the bottom of a large casserole dish. Top that with ¼ of the cheese and then spread ⅓ of the torn tortillas over the cheese. Repeat process 2 more times ending with a layer of tortillas. Spread remaining chicken pieces and cheese on top.
4 cup Mexican cheese blend
Bake until golden and bubbly, about 20-25 minutes. Let casserole cool for 5 minutes before cutting into serving size pieces. Serve warm.