Preheat oven to 350 degrees F.
In a large pot boil water for green beans. Boil green beans for 3-4 minutes, just enough to parboil them. Drain beans and rinse with cold water to stop the cooking.
In a large pan over medium heat, add and melt 2 tbsp of butter. Sprinkle flour into butter, then immediately whisk to combine well, for approximately one minute.
Add sugar and salt, and mix to combine. Reduce heat to low and add cream cheese. Mix until well combined and smooth. Turn off heat and add in sour cream, stirring until smooth.