In microwaveable container, microwave stock, cream and bay leaf until hot, about 1 to 1 ½ minutes. In saucepan over medium heat, melt butter. Stir in flour and cook and stir about 3 to 4 minutes to cook roux. Do not scorch. Slowly whisk hot broth mixture into roux. Simmer, stirring frequently, until thick and creamy, about 5 to 10 minutes. Remove from heat. Remove bay leaf. Blend in sour cream and seasonings.