Grease 2 (9-inch) round cakepans & flour lightly - or spray with Bakers Secret (nonstick cooking spray with flour).
Beat shortening and sugar together with an electric mixer. Add in the eggs, beating on medium speed.
Combine flour, cocoa, baking soda, & salt. Stir in the flour mixture & the buttermilk - alternating a little bit of each at a time, ending with the flour mixture. Beat 3 minutes at high speed, stopping once to scrape down sides. Stir in 2 teaspoons vanilla. Pour the batter into the prepared pans.
Beat cream cheese, 2 tablespoons butter, and cornstarch at medium speed until creamy. Gradually add the sweetened condensed milk, beating well. Mix in the egg & vanilla. Divide the cream cheese mixture between the two cake pans, pouring on top and spreading to evenly cover the cake batter.
Bake at 350 degrees for 40 minutes, or until a toothpick inserted in the center comes out clean. After removing from the oven, use a large spatula or wide knife as I did & press the risen cake down somewhat. Cool in pans on wire racks for 10 minutes; remove from pans & cool completely on wire racks.
Beat 2/3 cups butter until creamy. Add in the powdered sugar, cocoa, butter, vanilla extract & heavy cream. Stir until combined, and then beat at high speed until creamy. Spread frosting between the cake layers and on top and sides of the cake.