2sticks, 16 tablespoons unsalted butter, at room temperature
1 1/2cupspacked light brown sugar
1teaspoonpure vanilla extract
6ouncesbittersweet chocolate, chopped into chips or 1 cup chocolate chips
1cupcoarsely chopped walnuts
1cupsweetened shredded coconut
Preheat the oven to 325°F. Butter the bottom and sides of a 9-by-13-inch baking pan. Put a long piece of parchment paper in the bottom of the pan, letting the parchment extend up the two short sides of the pan and overhang slightly on both ends. Butter the parchment.
In a medium bowl, whisk together the flour, baking powder, baking soda and salt; set aside.
n the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed until smooth and creamy. Add both sugars and beat until well incorporated, about 3 minutes. Add the eggs one at a time, beating for 1 minute after each addition. Beat in the vanilla.
With the stand mixer on low speed, add the dry ingredients, mixing just until incorporated. Using a rubber spatula, stir in the chips, nuts and coconut. Spread into prepared pan and use an off set spatula to smooth the top.
Bake for about 40 minutes, until golden brown and a tooth pick inserted in the center comes out clean. Transfer the pan to a rack and cool for about 15 minutes before using the parchment handles to lift the bars out of the pan. Cool completely on wire rack before cutting into squares and serving.