In a skillet, melt the butter over medium heat until bubbling and fragrant. Add the diced serrano and jalapeño peppers along with the onion, sautéing until softened, about 3-5 minutes.

Stir in the minced garlic and cook for another minute, letting that delicious aroma fill your kitchen.

Sprinkle in the all-purpose flour, stirring continuously for 1-2 minutes to create a roux, which will help thicken the sauce.

Gradually whisk in the chicken broth, bringing the mixture to a gentle simmer.

Stir in the sour cream, salsa verde, cumin, salt, garlic powder, white pepper, cayenne, and half of the cilantro. Allow to simmer for about 5 minutes.

While the sauce simmers, preheat your oven to 350°F (175°C).

In a separate bowl, mix together the cooked chicken, shredded cheeses, and the remaining cilantro until fully combined.

Take each tortilla and fill it generously with the chicken mixture. Roll them up tightly and place seam side down in a greased baking dish.

Pour the luscious sour cream sauce generously over the enchiladas.

Place the dish in the preheated oven and bake for 25-30 minutes, or until the enchiladas are bubbly and golden brown on top.