Lightly coat a cookie sheet with cooking spray.

Mix flour and baking soda in a small bowl; set aside.

With a spoon, mix butter, peanut butter and brown sugar in a medium bowl until smooth.

Add egg and vanilla; beat until smooth.

Add flour mixture and stir until combined.

Cover dough and refrigerate for 20-30 minutes.

Preheat oven to 375 degrees Fahrenheit.

Roll dough into 1-inch balls and bake for 8-10 minutes.

Remove from oven and let stand for 10 minutes; allow to cool in the refrigerator for another 20-30 minutes.