1. Mix the chicken and barbecue sauce in a small saucepan over medium-low heat. Stir to combine. Heat until warmed through, 8-10 minutes.
2. Meanwhile, make the cheese sauce. Melt the butter in a large saute pan over medium heat. Add the flour, whisk to combine, making a roux, and stir for 1-2 minutes.
3. Slowly pour in the milk, whisking constantly. Cook for 1 minute until mixture is thick and bubbling.
4. Turn the heat down to the lowest setting and whisk in the cheese one small handful at a time. Whisk in all of the cheese and stir until smooth. Season to taste with salt, pepper, and cayenne.
5. Stir in the jalapeños.
6. Place a layer of tortilla chips on a serving plate. Top with the melted cheese. Spoon some of the barbecued chicken onto the cheesy chips.
7. Repeat, topping with more cheese. Garnish with black olives. Dollop the avocado and sour cream in the middle and serve.

Serves 1-2.