Spread the coconut on another rimmed baking sheet and toast in the oven until light brown and fragrant, about 7 minutes.
Keep checking every couple of minutes & stir as needed b/c the sides brown quicker than the middle of the sheet.
Set aside to cool.
Spray a 12 X 17-inch rimmed baking sheet with nonstick cooking spray, line with parchment paper, and spray again.
Set aside.
Sift together the flour and baking powder and set aside.
Melt the butter, bittersweet chocolate, unsweetened chocolate, salt, and cayenne, if so desired, together in a double boiler or in a heatproof bowl set over a saucepan of gently simmering water, stirring occasionally to blend.
When completely melted and smooth, remove from the heat.
Whisk eggs until frothy.
Add the sugar and continue to whisk until the mixture is pale yellow, thick, and doubled in volume.
Add the vanilla to the eggs and mix to incorporate.
Add 1/2 cup of the melted chocolate & mix to incorporate.
This will keep the eggs from cooking into chocolate scrambled eggs.
Then, in a slow, steady stream, add the rest of the melted chocolate and whisk to fully incorporate.
Fold in the flour mixture, the cooled toasted coconut, and chocolate chips.
Spread the batter evenly into the prepared pan and bake for 15 minutes, then rotate the pan and bake until a tester comes out barely clean, another 10 minutes.