Preheat the oven to 325 degrees F. Spray three 8-inch round cake pans with non-stick spray, line the bottom with parchment paper, and spray again. Set aside.
In a medium size bowl, whisk together the cake flour, baking powder, and salt. Set aside.
In the bowl of a stand mixer, fitted with the paddle attachment, beat the butter and sugar on medium-high until fluffy and smooth, about 3 to 5 minutes.
Add the eggs and egg whites, one at a time to the bowl and beat on medium until well incorporated. Stir in the mint extract.
Turn the mixer on low and add 1/3 of the flour mixture to the butter mixture and mix until fully incorporated. Then add half of the buttermilk, followed by another 1/3 of the flour mixture, the second half of the buttermilk and lastly, add the remaining flour mixture and mix until incorporated. Scrape down the sides of the bowl and mix on low for another 30 seconds.
Stir in the food coloring, if using, followed by the crushed Oreos.
Evenly distribute the cake batter among the three pans and bake for 25-30 minutes or until a toothpick inserted into the middle of the cakes comes out clean or with just a few crumbs. Make sure not to over bake.
Remove cakes from the oven and let cool in pans for 10 minutes before inverting onto cooling racks.
Once completely cooled, wrap in plastic wrap and place in the freezer or refrigerator to chill before frosting.