Position the 2 oven racks to divide oven in thirds; preheat oven to 325 degrees F. Line 2 cookie sheets with baking parchment or foil.
In a large mixing bowl, beat the egg whites, salt, and cream of tartar with an electric mixer set on medium speed until egg whites are foamy. Continue beating, gradually adding the sugar, 2 tablespoons at a time, until mixture forms firm but still moist peaks. Add the vanilla and beat just until blended. In 2 additions, fold the cocoa and cinnamon into the beaten whites just until blended (a few streaks may remain).
Drop heaping teaspoonfuls of the batter, 1 inch apart on the prepared baking sheets.
Bake the drops for 13 to 15 minutes until the tops have cracked and the centers are fairly dry. Cool on baking sheet on a rack for 10 minutes. Using a metal spatula, transfer drops to a rack to finish cooling.
When drops are cool, place the chocolate morsels in a metal bowl and set over a saucepan on gently simmering water. Stir until chocolate is almost melted.
Remove from heat and continue to stir until completely melted and smooth. Using a small pastry brush, apply a thin coating of chocolate onto the flat side of each drop.
Let the drops stand, chocolate-side up, until the chocolate has set. Store the drops in a tightly covered container for up to 3 days.