Spray two 8 inch round cake pans with non-stick spray or cake release. Add all ingredients to an electric hand or stand mixer.
Beat until well combined. Pour into prepared baking pans and set the temperature to 12 to 15 minutes, or until the toothpick comes out clean. Depending on how large your air fryer is, you may be able to get either 2 or 3 cakes out of this. I used 2 --6 inch round cake pans.
Remove from the air fryer and let cool for at least an hour. After an about, use a serrated knife to remove the "dome" from the cake. Wrap each cake in plastic wrap and freeze for at least 2 hours
Cream butter and shortening together. Add powdered sugar, vanilla, and half of the liquid to the bowl. Mix until incorporated. Add one drop of green gel food coloring (electric green is pictured, but mint or leaf green would work)
Finely chop 6-8 mint Oreos, add to the frosting, and add half of the remaining heavy cream. Mix on high for 5-7 mins, the frosting will double in size, the color will lighten, and the texture will become silky. Only add the last .05 tbsp of liquid if needed.
Add frosting to the first layer of cake (I used a standard-sized ice cream scooper for this). Use an offset spatula to spread buttercream on the cake. Add chopped Oreos to give it an extra crunch.
Place the top layer of cake over it sandwiching the frosting and Oreos. To reduce cake crumbs, always "frost the frosting." Using a large offset spatula, spread the frosting onto the side of the cake.
Once you make the initial frosting constant, as you move around the cake, only add frosting to frosting all the way around. It doesn't need to be smooth or perfect. Just frost the entire cake before removing any excess. Use a butter knife (or spoon), starting at the base of the cake pull in an upward diagonal motion to create a rustic design.
Smooth out the top of the cake with your offset spatula. Add additional frosting to a piping bag fitted with a 1M tip. Place Mint Oreos around the top of the cake and fill in the gaps with piped buttercream.
Plate, serve, and enjoy!