Preheat oven to 350 degrees. Beat butter and cream cheese at medium speed with mixer until creamy. Gradually add in sugar, mixing until mixture becomes light and fluffy. Add eggs, one at a time, mixing after each egg addition. Next combine flour, baking soda, baking powder and salt. Once blended, gradually add in butter to the mixture. Beat at a low speed until the mixture is completely blended.Once blended stir in bananas, vanilla and nuts withe mixing spoon by hand. Spoon batter into two greased and lightly floured loaf pans. Bake at 350 degrees for 1 hour. Once golden brown and completely baked in the center, remove from oven and let cool for 20 minutes. If you desire, you make make a glaze consisting of 1 cup powdered sugar and milk, mix well, and drizzle over warm bread. Cool for another 30 minutes before slicing.