Melt the butter then stir in the flour and cook for about a minute, until it turns from clumpy to smooth.
Add the minced garlic and stir in the chicken broth. Bring to a boil and cook for 5 minutes, stirring frequently.
Once the sauce has thickened, remove it from heat and stir in the sour cream, jalapenos, cumin, salt, and pepper.
Spray your 9x13 pan with nonstick cooking spray, then place 6 tortillas in the bottom of the baking dish. It's okay for them to overlap some.
Cover the tortillas with half of the chicken.