Grease two 9x13 pans and line the bottom with parchment paper.
Add flour, sugar, cocoa powder, salt, baking powder and baking soda to your mixing bowl (I use a stand mixer with the whisk attachment). Stir until combined.
In a separate medium bowl, whisk together the oil, buttermilk, eggs and vanilla. Once combined, add in the coffee slowly so you don't cook the eggs.
Pour the wet ingredients into the dry ingredients and stir slowly until combined. Then mix on high for two minutes, scraping the sides halfway through.
Distribute the batter evenly between the two prepared pans and bake for 20-25 minutes, or until a toothpick comes out clean. (A few moist crumbs sticking to the toothpick is fine, but you don't want it gooey)
Cool cakes for a few minutes. Run a butter knife around the outside of each pan, and turn the cakes out onto a cooling rack and carefully remove parchment paper. Let cool completely.
Make the Filling
In a saucepan, mix flour and milk with a whisk. Bring to a boil, stirring constantly, until thick. Remove from the heat and let cool.
In a large bowl (or stand mixer with a whisk attachment), beat the shortening, butter, sugar, salt and vanilla until fluffy.
Add the cooled milk mixture and beat until smooth.
Place one of the cakes back into the pan, spread filling over the cake and top with the other cake layer.
Make the Ganache Topping
Place chocolate in a medium sized bowl.
In a microwave safe bowl (or glass liquid measuring cup), heat the heavy whipping cream in 15 second increments until it's very hot but NOT boiling.
Pour the cream over the chocolate chips and let sit for two minutes.
Add the corn syrup and stir until smooth and glossy. Pour over the cake and spread with a spoon.
Refrigerate cake for at least 2 hours to let everything set. Enjoy!