Remove all the skin and bones from the cooked rotisserie chicken and discard. Shred or chop the meat and set aside.
In a large pot or Dutch oven, cook the onion over medium-high heat in 2 tablespoons of butter until softened. Remove from the pot and set aside.
In the same pot, melt the remaining 6 tablespoons of butter over moderately low heat and whisk in the flour.
Cook, whisking constantly, for about three minutes.
Stir in the onion.
Gradually add the broth then the half and half, whisking constantly until well blended.
Bring the mixture to a boil, reduce the heat, and simmer, stirring occasionally, for 5 minutes, or until thickened. (It will be nicely and obviously thick.)
Stir in Tabasco, chili powder, cumin, salt, and pepper.
Add beans, chilies, chicken, cheese, and milk.
Cook over moderately low heat, stirring occasionally for 20 minutes.
Add sour cream.
May be served immediately but is even better served the next day.
To serve – ladle the chili into bowls and top with the usual chili garnishes–cilantro, cheese, lime wedges, jalapenos, etc.
