Banana Sour Cream Cake

{I think I got this out of the Cit Pat. It's yummy!}

1 pkg yellow cake mix

3 eggs

1 cup mashed ripe banana (about 3 bananas)

1 cup sour cream

1/4 cup oil

18 oz cream cheese, softened

1/2 cup butter, softened

4 cups powdered sugar

1 cup walnuts, finely chopped

Beat first 5 ingredients with a mixer on low until moistened, scrapping bottom of bowl. Beat on medium speed for 2 minutes. Pour into a greased and floured 9X13 in. pan. Bake @ 350* for 35 minutes or until toothpick inserted in center comes out clean. Cool cake in pan on wire rack.

For frosting: Beat cream cheese and butter with mixer on medium until blended. Gradually add sugar, beating well after each addition.

Remove cake from pan. Cut cake crosswise in half using serrated knife. Place one cake half on plate, spread frosting on top. Top with remaining cake half. Frost top and sides, press nuts onto sides. Refrigerate leftovers.