Cream shortening and sugar until fluffy. Add eggs and beat for 1 minute. Put cocoa and food coloring in a cup and make a paste; add to mixture. Add salt. Put 1 teaspoon vanilla in buttermilk and add slowly to mixture alternately with flour. Combine vinegar and soda in a cup and mix thoroughly. Blend this into batter, but do not beat. Bake in 2 (9-inch) layer cake pans at 350° for 25 to 30 minutes. Cool on racks. Cut layers in half horizontally, making 4 layers.

Frosting: Cook milk and 5 tablespoons flour until thick. Place in refrigerator until ready to use. Beat together 1 cup butter, 1 cup powdered sugar and 1 teaspoon vanilla. Beat until creamy. Add milk mixture, a little at a time, beating until fluffy. Frost between layers and top, but not sides of cake.