1. Grease a 9×13 cake pan and preheat oven to 350 degrees.
1. Beat butter and sugar until light and fluffy, about 3-4 minutes.
2. Add vanilla, sour cream and vegetable oil and mix until well combined.
3. Add eggs and egg white in two batches, mixing until well combined.
4. Combine dry ingredients in another bowl.
5. Add half of the dry ingredients to the batter and mix until well combined.
6. Add the mashed bananas and mix until well combined.
7. Add remaining dry ingredients and mix until well combined.
8. Pour batter into cake pan and bake 34-36 minutes or until a toothpick inserted comes out with a few crumbs.
9. Allow cake to cool completely.
10. To make frosting, beat cream cheese and butter until smooth.
11. Add half of the powdered sugar and beat until smooth.
12. Add vanilla extract and water and beat until smooth.
13. Add remaining powdered sugar and beat until smooth.
14. Frost the cake with the cream cheese frosting.
15. Use a piping bag and tip (I used Ateco 844) to pipe swirls around the outer edge of the cake and garnish with banana chips.