Preheat your oven to 350°F (180°C) and line baking sheets with parchment paper or silicone baking mats. Set them aside for later use.
In a medium bowl, whisk together the all-purpose flour, graham cracker crumbs, baking soda, and salt until well combined, then set the mixture aside.
In a large mixing bowl, cream the softened butter, granulated sugar, and light brown sugar on medium speed for 2–3 minutes, until the mixture is light in color and fluffy. You should visibly see the texture lighten—this is a sign it’s properly creamed.
Add the egg and mix until fully incorporated. Then add the vanilla extract and mix again until combined.
Gradually add the dry ingredients to the wet mixture and mix just until a thick dough forms. Be careful not to overmix. Once everything is incorporated, use a rubber spatula to help bring the dough together into a cohesive, uniform ball.
Scoop out about 6 tablespoons (105g) of dough per cookie to form large cookie dough balls—you should end up with around 8 balls total. Roll each dough ball in the additional 1/4 cup (34g) of graham cracker crumbs to coat the outside.
Arrange the dough balls on your prepared baking sheets, spacing them well apart. Bake 4 cookies at a time for best results. Use the bottom of a cup or a similar flat surface to gently press each dough ball down slightly. They will spread during baking, so they only need a light press. After pressing, the cookie dough balls should measure roughly 2½ inches across and may show a few cracks around the edges.
Bake the cookies for 12–15 minutes, or until the edges are lightly golden and the centers appear set.
Let the cookies cool on the baking sheet for 5–10 minutes before transferring them to a wire rack. Allow them to cool completely before applying any toppings.