Preheat oven to 350 degrees, grease two round 9'' cake pans or one 13x9 pan, set aside.
Cream butter and sugar together in a large bowl, Add eggs and mix well, Add flour and baking soda and mix until combined. Next add the mashed bananas, milk and vanilla and mix well.
Pour batter into two prepared 9 inch pans. Bake at 350 degrees for 25-30 minutes, or until a toothpick comes out clean. Cool in pan for 5 minutes, remove to cooling rack to finish cooling.
For the Frosting:
Beat the butter and cream cheese with an electric mixer on high. Next lower the speed to low and add the powder sugar half a cup at a time until it is fully combines. Beat in the vanilla extract