Grease and line with parchment paper one 8″ X 3″ round cake pan or two 6 X 3″ round pans to make a tiered cake.
Cream butter and sugar. Mix in eggs one at a time. Add vanilla and mashed bananas. Sift flour, baking powder and salt together and add to wet ingredients alternately with soured milk. Pour into prepared pans and bake for 80-90 minutes or until done.
Let cool slightly in pan then turn out onto cooling rack
1 cup butter
4 cups icing sugar
4 tsp. vanilla
Cream (use as much as needed until icing is light and fluffy)