Preheat the oven to 325 degrees. Line a 8 in square baking pan with foil and then coat with cooking spray.
In a small bowl, combine flour, cocoa, salt, and baking powder.
In another medium bowl, combine nut butter, maple syrup, egg, and vanilla. Stir in dry ingredients until just moistened. Fold in walnuts and chocolate chips.
Pour into the prepared pan and bake for 30 minutes. Allow to cool in the pan before removing the foil and cutting into bars.
Notes
I grind old fashioned oats myself in a food processor. You can also purchase your own.