How to Make Chocolate Oreo Cake with Cocoa Buttercream:
In the bowl of a stand mixer with the whisk attachment, or with a hand-held mixer, beat the sugar, vanilla extract and oil until fluffy, about two minutes.
In another bowl, sift together the flour, baking soda, baking powder, coffee, cocoa powder and salt.
Add the cocoa-flour mixture to the wet ingredients in three batches, alternating with the almond milk-vinegar mixture, beating 20 seconds after each addition. Scrape down the sides and the bottom of the bowl after each addition to ensure everything is mixed together. Don't overbeat.
Line two 9-inch cake pans with parchment paper at the bottom, and oil and flour the bottom and sides. Divided the cake batter evenly between the two pans.
Bake in a preheated 350-degree oven for 40 minutes or until a toothpick stuck in the center of each cake comes out clean.
Cool the cake pans on a rack for 15 minutes. Then run a knife along the edges of the cake pans and unmold the cakes by putting a plate over the mouth of the pan and flipping it. Peel off the parchment paper.
Place the unmolded cakes on the rack to cool completely.
For frosting, have your butter and shortening at room temperature. Place them in a bowl and with a hand mixer or in a stand mixer with a whisk attached, beat until you have a fluffy mixture, about a minute.
Add the confectioners' sugar in batches of 1/4 cup at a time, beating about 20 seconds after each addition. As with the batter, scraped down the sides and bottom of the bowl after each addition to ensure everything is evenly mixed.
Remove 1/3rd of the frosting to another bowl. Add the vanilla extract and mix well. Set aside. This is your vanilla butter cream frosting.
Add the cocoa powder and instant coffee powder to the remaining butter cream and mix well. This is your chocolate butter cream frosting.
Place one cake on a cake stand or a plate and top with the vanilla butter cream. Using a table knife or a spatula, spread the frosting evenly on top of the cake.
Place the second cake on top of the first one. Top with the chocolate butter cream and spread it evenly on top of the cake and on the sides.