Light, marshmallowy centred, have a crunch from the cocoa nibs, and all around perfect treat!
Space 2 racks evenly in the middle of an oven and preheat to 350° F. Line 2 baking sheets with parchment paper.
In a heatproof bowl, whisk together egg whites and sugar. Set over, but not touching, simmering water in a pot. Whisk constantly until the sugar is completely dissolved. (This took me close to 7 minutes.) Remove from heat.
Using an electric mixer fitted with the whisk attachment, beat the egg mixture on high until stiff and glossy, about 4-6 minutes. Sift the cocoa powder over the meringue. Sprinkle with the chocolate pieces and cocoa nibs. Fold together gently with a rubber spatula until combined.
Drop the meringue by heaping tablespoon, spaced slightly apart, onto the baking sheets.
Bake for 18 minutes, rotating the pans halfway, until the meringues are fluffy, full of cracks, and spring back up when touched. Remove from oven and carefully pick up the parchment paper sand transfer the meringues, still on the parchment, to wire racks to cool.