Preheat the oven: Set your oven to 350°F and line baking sheets with parchment paper or silicone baking mats.
Cream butter and sugars: In a large mixing bowl, beat the butter, white sugar, and brown sugar together for 2–3 minutes until light and fluffy.
Add egg and vanilla: Beat in the egg and vanilla extract for another 2–3 minutes until fully incorporated.
Mix dry ingredients: In a separate bowl, whisk together the graham cracker crumbs, cocoa powder, flour, baking soda, and salt.
Combine wet and dry: Add the dry ingredients to the butter mixture, mixing just until combined. Avoid overmixing so the cookies stay soft.
Scoop the dough: Use a cookie scoop to drop tablespoonfuls of dough onto prepared baking sheets.
Bake and cool: Bake for 9–11 minutes, until the edges are set but the centers are still slightly soft. Let cool on the pan for 5 minutes before transferring to wire racks.