Melt 2 tablespoons of the butter in a skillet over medium-low heat. Add the smashed garlic and cook for 2-3 minutes.
Add the chopped poblano peppers and chipotle peppers. Cook for 10 minutes, stirring occasionally.
Add the remaining 1 tablespoon of butter and let it melt. Stir in the flour and cook for 1-2 minutes to create a roux.
Gradually whisk in the chicken broth and milk. Bring to a simmer and cook until thickened, about 5-7 minutes.
Remove from heat and stir in the onion powder, chicken bouillon, and salt. Blend the sauce until smooth using an immersion blender or food processor.
Return the sauce to the pan and keep on low heat. Stir in the chopped cilantro.
In a bowl, mix together the shredded chicken, diced green chiles, and 1 cup of the colby jack cheese.
Spread a thin layer of the sauce in the bottom of a 9x13 baking dish. Dip the corn tortillas in the sauce, one at a time, and fill them with the chicken mixture. Arrange the filled tortillas seam-side down in the baking dish.
Pour the remaining sauce over the enchiladas and top with the 2 cups of shredded pepper jack cheese.
Bake at 375°F for 20 minutes, or until the cheese is melted and the sauce is bubbling.
