For the sauce: In medium saucepan over medium heat, add the butter, garlic and jalapeno. Saute for 3 minutes, and then sprinkle in the flour. Cook, stirring frequently, until you create a blond roux, about 5 minutes. Add the milk, cheese and mustard and use a whisk to stir all together. Season with salt and pepper and let cook for 5 minutes on low.
For the nachos: Shred the chicken and place into a medium bowl. Pour in the barbecue sauce and mix well to combine. Arrange the tortilla chips on a platter and spread the chicken over the chips. Pour the warm cheese sauce over the top and sprinkle with the jalapenos and cilantro. Garnish with dollops of the sour cream.
Recipe courtesy of Aaron McCargo Jr.