Preheat oven to 350°. Spread nuts on a large rimmed baking sheet and bake until deep golden brown, 10 to 15 minutes. Transfer nuts to cutting board to cool; chop coarsely and set aside. The recipe also directs you to toast the coconut on same rimmed baking sheet, stirring 2 to 3 times, until light golden, about 5 to 7 minutes, but note: I do not toast the coconut.Fit two pieces of aluminum foil into a 13 by 9" baking pan, pushing it into corners and up sides of pan; allow excess to overhang pan edges.Spritz evenly with nonstick cooking spray. NOTE: It's important to line the pan with foil because you want to be able to remove the bars from the pan by simply lifting the foil overhang on both sides. Then, you can peel down the foil and slice them perfectly.Whisk flour, baking powder, and salt together in a medium bowl; set aside.Whisk melted butter and brown sugar together in medium bowl until combined.Add eggs and vanilla and mix well.Using rubber spatula, fold dry ingredients into egg mixture until just combined; do not overmix.Fold in chocolate, coconut, and nuts. NOTE: I like to toss the three add-ins together in a bowl before adding them to the batter so that I can ensure an even dispersal.Turn batter into prepared pan, smoothing top with rubber spatula.Bake until top is shiny, cracked, and light golden brown, 22 to 25 minutes; do not overbake. Cool on wire rack to room temperature. Remove bars from pan by lifting foil overhang and transfer to cutting board. Cut into 2-inch squares and serve.