Preheat the oven to 350 degrees F (180 degrees C). Grease a 9x13-inch pan.

Combine flour, walnuts, baking powder, salt, and baking soda in a medium bowl. Set aside.

Mix together brown sugar and melted butter in a large bowl until combined. Beat in eggs and vanilla. Stir in flour mixture. Pour batter into the prepared pan. Sprinkle top with chocolate chips.

Bake in the preheated oven until a toothpick inserted into the center comes out with a few crumbs, 20 to 25 minutes. Allow to cool, then cut into 24 bars.