Step 1

Preheat oven to 350°F. Prepare two 8 inch round cake pans by spraying the insides with cooking spray and cutting round pieces of parchment paper to line the bottoms of the pans.*(SEE NOTES) Set aside.

Step 2

In a medium bowl, combine flour, cocoa powder, sugar, baking soda, baking powder, and salt and whisk together until most clumps are gone.

Step 3

Add in the milk, water, oil, vanilla extract, and vinegar and mix until lumps are gone.

Step 4

Evenly divide the batter between the prepared pans. Bake for 18-30 minutes, or until a toothpick inserted in the middle of the cake comes out clean.

Step 5

Place the cake pans on a cooling rack and leave the cakes in the pans until they've cooled completely. When removing the cakes from the pans, run a knife around the edges and turn them upside down onto the cooling rack. While they cool, make the buttercream.

Step 6

Leave the filling in the Oreos and crush them up using a blender or food processor. You can also put them in a ziploc bag and go over them with a rolling pin. Set the crushed Oreos aside.

Step 7

In a medium bowl, use a handheld mixer or standing mixer to mix the vegetable shortening and vegan butter together until they are smooth. If there are a few small chunks of shortening you can smooth them out using a spatula.

Step 8

Add in the vanilla extract and salt, then slowly add in the powdered sugar, 1/2 cup at a time until it reaches your desired consistency. If it seems too thick, add in about 1-2 tsp of milk to thin it out.

Step 9

Mix in the crushed Oreos and chill covered in the fridge until you're ready to assemble the cakes.

Step 10

Remove the (completely cooled) cakes from the pans. Run a butterknife around the edges of the cake to make this easier.

Step 11

Use a serrated knife to flatten the top of the cakes if they have domed. This will create a more even, upright cake.

Step 12

Place the thickest cake on the cake plate, cake stand, or cake board and top it will buttercream. Spread the frosting towards the edges of the cake, leaving about and inch of space before it reaches the edges.

Step 13

Place the second layer of cake on top, then freeze the cake for 15 minutes (this is optional). Use the back of an offset spatula to frost the outside of the cake, then smooth it out with a bench scraper. Unless you ground the Oreos up really fine, the frosting won't be completely smooth because of the cookie chunks.

Step 14

Frost the top of the cake and then top with more Oreo crumbs, big pieces of Oreo cookie, and/or whole Oreos if desired.