Preheat oven to 300 degrees. Line a cookie sheet with parchment paper.
Add the egg whites and cream of tartar to a large bowl. Beat with a hand mixer or with a stand mixer on high until soft peaks form.
Gradually add in the sugar while continuing to beat until stiff peaks have formed. Pull out the beater to check for stiff peaks. If the meringue can stand straight up on your beater or in the mixing bowl, you're ready. Do NOT under mix or your cookies will be puddles. If you aren’t sure, beat the meringue just a little more.
Sift the hot cocoa mix over the meringue and very carefully FOLD it in. Do not stir the mixture, it will cause the meringue to weep.
Fold the chocolate chips in with just a few folds. The less you work the meringue, the better it will set.
Using a 1 1/2 tablespoon cookie scoop, scoop round mounds of batter onto the prepared cookie sheet spacing the cookies 2 inches apart.
Sprinkle with the chocolate sprinkles or mallow bits.
Place in the oven and bake for 20-23 minutes. Once you start to see the edges brown a little, turn the oven off and let them sit in there for about 30 minutes. Do not take them out until they are completely dried.
Place onto a sheet of wax paper to cool and store in an airtight container at room temperature.