Step 1Heat the oven to 150 degrees.
Step 2Line 2 baking sheets with parchment and, using a pen, trace 20 (2-inch) circles onto each sheet (your final count will depend on the volume of your meringue; you may not fill all of the circles). Turn the parchment over so the ink won't bleed into the meringues.
Step 3Place the egg whites and cream of tartar in the bowl of a stand mixer fitted with the whisk attachment (alternatively, this can be done in a large bowl with a hand mixer). With the mixer on low, beat the whites gently just until frothy, about 2 minutes.
Step 4With the mixer still on low, gently sprinkle in 4 tablespoons of the sugar. Continue to beat until the whites start to thicken to a meringue but are still shy of having soft peaks, about 10 minutes.
Step 5Sprinkle over 4 more tablespoons sugar and keep beating until the meringue forms medium-firm peaks (they should not be stiff), another 10 minutes.
Step 6Sprinkle over the remaining 2 tablespoons sugar and continue to beat until the meringue is glossy and smooth and almost stiff, 6 to 8 minutes.
Step 7Sift one-third each of the cocoa powder and powdered sugar over the meringue and gently fold them in. Continue until all of the cocoa and sugar have been incorporated. Gently fold in the peppercorns and cacao nibs.
Step 8Transfer the meringue to a pastry bag fitted with a large round tip (about one-half inch in diameter). Pipe the meringue onto each of the circles. To do this, hold the pastry tip about one-half inch over the center of each circle and pipe the meringue, pressing until it spreads to the edge of the circle. Lift the pastry tip slightly and cut the pressure, forming a "peak" over the center of each meringue. Continue until all of the meringues have been piped.
Step 9Place the meringues in the oven and bake until they have formed a hard shell, about 2 1/2 hours. Rotate pans every hour for even baking.
Step 10Cool the meringues completely, then store in an airtight container in a dry, cool place. The meringues will keep for up to 2 days.