Heat oven to 350°F.
Grease and flour two round cake pans.
Using a mixer, cream the shortening and sugar until fluffy.
Add eggs and beat for one minute. Set aside.
In a separate cup, place cocoa and food coloring and make paste.
Add to the creamed sugar mixture. Add salt.
In a separate bowl, combine vanilla and buttermilk and add flour slowly. Set aside.
Next, put the vinegar and soda in a cup and mix.
Add the flour mixture to the creamed sugar mixture.
Fold ingredients together, do not beat. Pour batter into greased pans and place into preheated oven.
Bake at 350° for 25 to 30 minutes.
Combine milk and flour.
Cook in a saucepan over medium heat and cook the mixture until it is thick.
Put in a bowl and place in the refrigerator to cool.
Beat remaining ingredients with mixer.
Incorporate flour and milk mixture a little at a time.