Preheat oven to 350F and line a baking sheet with parchment paper.
In a bowl, mix all cookie ingredients until you have a cookie dough.
Scoop the dough into tablespoon sized balls and place on the prepared baking sheet. Using a teaspoon, press into each cookie to create the "thumbprint" indentation.
Bake the cookies for about 10-11 min. If the indent has slightly disappeared, gently press with a teaspoon again. Let cool while you mix the fudge filling.
Melt together the nut butter and chocolate until smooth (I use 30 sec intervals in the microwave). Spoon the filling into the center of each cookie and allow them to set in the fridge for about an hour. Enjoy!