In a heatproof bowl set over a pan of barely simmering water (bottom of bowl should not touch water), stir chopped chocolate and butter often until chocolate is melted and mixture is smooth. Remove from over water and let cool to room temperature, about 15 minutes.
In a large bowl, with an electric mixer on high speed, beat sugar, eggs, and vanilla until smooth. Add chocolate mixture and beat until well blended. Stir in flour and baking powder, then beat just until moistened. Stir in macadamia nuts, chocolate chips, and coconut.
Drop dough in 1-tablespoon portions, about 2 inches apart, onto buttered or cooking parchment-lined 12- by 15-inch baking sheets.
Bake cookies in a 350° oven just until firm on the edges but still soft when pressed in the middle, 8 to 10 minutes (see notes); if baking more than one pan at a time, switch pan positions halfway through baking. Let cookies cool on sheets for 5 minutes, then use a wide spatula to transfer to racks to cool completely.
Note: Nutritional analysis is per cookie.