Preheat the oven to 350 F. In a medium bowl, whisk together flour, salt, and baking soda. In a large bowl, mix together butter and sugar until fluffy. Add in the egg and mint extract.
Add in the flour mixture, mix until it is fully combined. Fold in the crushed Oreo cookies. Press the cookie dough into a greased 8-inch square baking dish. Bake for 20-25 minutes.