Preheat the oven to 325 degrees. Line a baking sheet with parchment paper or a silicone baking mat.
In a medium mixing bowl, stir together 6 ounces of the cream cheese with 1 tablespoon erythritol and the vanilla until smooth. Transfer to a plastic bag or pastry bag.
Beat the egg whites with the cream of tartar and 4 tablespoons erythritol until stiff peaks form. Beat in the cocoa powder.
Beat the egg yolks and remaining 2 ounces of cream cheese together until smooth. Take about ¼ of the egg whites and stir into the egg yolk mixture, then gently fold in the rest of the egg whites.
Spoon 6 mounds onto the prepared baking sheet. With the back of a spoon, flatten the mounds slightly and make a shallow indentation in the center of each. Pipe the cream cheese mixture into the center.