Pre-heat oven to 350. Sift dry ingredients into a bowl and stir together
Add shortening, mashed bananas, and sour milk. Mix until flour is dampened. Beat vigorusly for 2 minutes.
Add 2 eggs and beat 2 minutes longer
Stir in 2/3 cup of chopped walnuts.
Pour cake mix into two 9" round pans (be sure to grease and lightly flour them. Bake at 350 for about 18 to 20 minutes. Insert a toothpick and if it comes out clean, remove from oven and cool for 10 minutes. If not, give the cake a couple more minutes until the toothpick comes out clean.
After 10 minutes of cooling invert cake onto a wire rack and completely cool before frosting.