Preheat the oven to 350 degrees F. Line a 13x9” baking pan with foil, leaving an overhang so that you can easily remove the bars when they're cooled.

Whisk flour, baking powder, and salt in a medium bowl and set aside.

Beat the melted butter and brown sugar until well combined, about 1 full minute.

Beat in the eggs and vanilla.

Stir in the flour mixture, being careful not to overmix.

Stir in the coconut, both types of chocolate chips, and the walnuts. Spread the mixture evenly into the prepared pan and smooth the top. Bake for about 23 minutes, or until the top is shiny and looks firm.

Let the pan cool completely on a wire rack. Cut into 24 bars.