Preheat oven to 350. Grease two 9-inch round pans.

In a stand mixer: beat shortening and sugar together until light and fluffy.

Add eggs one at a time and beat well after adding each one.

Add in the salt, vanilla, buttermilk, sifted flour and cocoa powder to the batter.

Add in the green food coloring gel to the creamed mixture. Add in the desired amount of food coloring gel until the right color green is achieved.

Mix baking soda and vinegar together, then gently fold it into the cake batter. Only stir the batter after this step.

Pour the batter into the prepared pans. Bake in preheated oven until a tester inserted into the cake comes out clean, about 30 minutes. Cool the cakes completely on a wire rack.

In a saucepan cook the milk over low heat. Add in the flour and mix together until thick. Stirring constantly. Let the milk flour mixture cool completely.

While mixture is cooling, beat sugar, crisco, butter, salt and vanilla until light and fluffy. Add in cooled milk flour mixture in and beat until frosting is spreadable. When the cake is completely cooled, frost the cake layers.

Decorate for St. Patrick's Day: Add a little sugar and green food coloring together and free hand a shamrock on top of the cake for a cute decoration.