Preheat oven to 325 degrees F (165 degrees C). Grease and flour 2 round 8 inch pans. Sift the flour and salt together and set aside.
Cream butter and sugar until light and fluffy. Add eggs and mix well. Dissolve baking soda in buttermilk. Alternately add flour and buttermilk, beginning and ending with the flour. Pour into two 8-inch pans.
Bake at 325 degrees F (165 degrees C) for about 30 minutes, or until toothpick inserted into cake comes out clean. Cool cake completely before icing.
To make the White Velvet Cream Cheese Icing: Beat shortening and cream cheese together. Gradually beat in confectioners sugar. Add milk until a frosting is formed. (Add more milk if necessary.)