4. To make the chocolate filling, whisk together powdered sweetener and eggs in a saucepan over low medium heat, stirring constantly. Heat until the egg mixture reaches 150-160 degrees or until it coats the back of a spoon. Don’t over cook or your eggs will curdle. (See information below on how to salvage your custard if your eggs curdle.) Remove from the heat and stir in melted chocolate and vanilla. Set aside.