Preheat oven to 350. Line a 9x9-inch square baking pan with parchment paper and spray with nonstick spray.
Whisk together flour, baking soda and salt and set aside.
Cream the butter for one minute until light and fluffy. Add in the brown sugar and sugar and mix for 2 minutes or until the mixture feels smooth between your fingers.
Mix in the egg and vanilla.
Slowly mix in the flour mixture until incorporated.
Fold in chocolate chips and 1 cup chopped Snickers.
Press the mixture into the bottom of the prepared pan to form an even layer. Sprinkle the remaining chopped Snickers. Bake for 35-40 minutes, or until cookie dough has turned a golden browned. Allow to cool completely.