In a large mixing bowl, beat your butter with an electric mixer for approximately 30 seconds. Add sugar, baking soda and salt; beat until combined. Beat in bananas, eggs, sour cream and vanilla. Stir in flour. Spread in a greased 15x10x1 baking pan.
Bake at 350 for 25-30 minutes. Let cool.
Beat cream cheese and butter until smooth. Beat in powdered sugar and vanilla until combined.
Spread over cooled top and cut into bars. Cover and store in refrigerator. Decorate as desired.