Preheat oven to 350° F. Line two 9x13 cake pan with parchment paper and grease with nonstick spray.
In a small bowl, whisk together the flour, graham cracker crumbs, and baking powder and set aside.
In a large bowl or the bowl of a stand mixer, cream together the butter and sugar until pale and fluffy on medium-high speed.
Add the eggs, one at a time, beating well between each addition.
Mix in the vanilla extract.
Add the flour mixture and the buttermilk, alternating between each and beginning and ending with the flour mixture. Make sure to scrape the bowl in between mix-ins.
Pour batter evenly into the prepared pans. Bake for about 15 minutes (or until golden brown and starting to pull away from the sides of the pans).
Cool in the pans for at least 15 minutes, then turn out onto a rack to cool completely. Cut out 28 total rounds using a 2.5-inch circle cookie cutter.