(If making cake by hand, mix cocoa, salt, flour and soda in separate bowl) Place shortning, sugar, eggs, sour milk and vanilla in bowl. Stir well. Mix very well the cocoa, salt, flour and soda. Add to first mixture gradually and beat thoroughly. Slowly add the boiling water and mix until smooth. If making cake in an electric mixer, add water by hand first, then turn on machine so doesn't splash. Before pouring batter into pan, grease and flour pan and then line pan with wax paper. Bake in 3 well greased 8 inch layer cake pans in 350 degree oven for 25-30 min. For 8x12 pan on 2nd shelf of oven, takes about 45 minutes. Remember, overcooking impairs the flavor of chocolate.