In a mixing bowl, combine the softened cream cheese, powdered erythritol, cocoa powder, and vanilla extract. Mix well until all the ingredients are thoroughly combined and smooth.
Place the mixture in the refrigerator for about 30 minutes to firm up.
Line a baking sheet with parchment paper. Remove the cream cheese mixture from the refrigerator and scoop out small portions, approximately 1 tablespoon each, and roll them into balls.
Place the balls onto the prepared baking sheet. Repeat until all the mixture is used.
Place the baking sheet with the cream cheese balls in the freezer for about 30 minutes, or until they are firm.
Meanwhile, melt the dark chocolate in a microwave-safe bowl in 30-second intervals, stirring well after each interval, until the chocolate is completely melted and smooth.
Take the cream cheese balls out of the freezer. Using a fork or toothpick, dip each ball into the melted chocolate, making sure it is fully coated. Gently tap off any excess chocolate and place the coated truffle back onto the baking sheet.
If desired, sprinkle the truffles with toppings such as unsweetened cocoa powder, crushed nuts, or shredded coconut.
Place the baking sheet with the coated truffles in the refrigerator for about 1 hour, or until the chocolate coating is set.
Once the truffles are firm, transfer them to an airtight container and store in the refrigerator until ready to serve.