Preheat the oven to 350 degrees. Grease a 24-cup mini muffin tin with baking spray. Set aside.
Beat butter, granulated sugar, and brown sugar together until well combined (using a standing mixer, hand mixer, or by hand).
Add in the egg, and mix until combined.
Add in vanilla extract, baking soda, and salt, mixing until combined.
Next, add in graham cracker crumbs and flour. Mix until well combined.
Using a 1” cookie scoop (about 1 Tbsp) disperse dough evenly between the muffin cups.
Bake for 9-10 minutes, or until the tops are lightly golden and the centers have risen (once you take the cookie cups out of the oven, the centers might sink a bit, which is fine).
Immediately, or within a couple of minutes, press centers down to form a cup shape (I used a tsp to do this).
Allow to cool completely.