In a large skillet, melt butter over medium heat. Add onion and cook, stirring occasionally, until the onion softens and starts to turn translucent, about 3-4 minutes. Sprinkle flour over the onions and stir well. Cook for 1 minute, stirring. Slowly whisk in the chicken broth and milk. Add salt, pepper, and cumin. Cook over medium heat until mixture is bubbling and thickened, about 4-5 minutes. Remove skillet from heat and stir in enchilada sauce and sour cream.

Spread about 1/4 cup sauce on the bottom of prepared dish. Fill each tortilla with about ½ cup chicken/cream cheese filling. Top with a small handful of shredded cheese. Save at least 1/2 cup cheese for the top of the enchiladas. Roll tortillas up and place seam side down in baking dish. Continue filling 8 enchiladas until dish is filled. Pour white sauce over top of enchiladas and top with remaining cheese. Bake 20-30 minutes until sauce is bubbling and enchiladas are lightly browned. If desired, sprinkle fresh cilantro over the top and serve.