Melt butter in a large, heavy bottomed stock pot over medium high heat.
Add flour and whisk to combine. Continue to cook for just a minute or two until the flour is absorbed by the butter and the mixture gets a bit bubbly and foamy and releases a bit of a nutty aroma.
Add half of the chicken stock to the pot and whisk briskly to combine. Continue to stir until the mixture thickens. This will take a couple of minutes.
When the mixture has become thick, add the remaining chicken stock to the pot and whisk well to combine. Continue to stir until it reaches the desired thickness. You will be able to tell when this is thick enough when the mixture coats the back of a wooden spoon and will not come back together when you swipe your finger through it.
Turn the heat down to medium low and add 1 cup of cream. Stir to combine. If you desire a thinner or richer soup, you can add the remaining cup of cream.
You can also add shredded or chopped, cooked chicken back to the soup if you are going to use it for a main course. Sautéed mushrooms with brandy would be a very nice addition. Sprinkle with some fresh chopped chives and serve.