Preheat oven to 225º.
Place the chocolate in a medium microwave-safe bowl; microwave at HIGH 45 seconds or until almost melted, stirring until smooth. Cool completely.
Cover a large baking sheet with parchment paper; secure with masking tape. Sift together 1/3 cup powdered sugar and cocoa.
Place egg whites and cream of tartar in a medium bowl; beat with a mixer at medium speed until soft peaks form. Increase speed to high, and gradually add granulated sugar and then cocoa mixture, 1 tablespoon at a time, beating until stiff peaks form. Add 1/2 cup of egg white mixture to melted chocolate; beat just until blended. Add chocolate mixture to remaining egg white mixture, and beat just until blended.
Drop 30 mounds onto prepared baking sheet.
Bake at 225º for 1 hour and 15 minutes. Turn oven off; cool meringues in closed oven 1 1/2 hours or until dry. Carefully remove meringues from paper.
Combine peanut butter and remaining ingredients, stirring with a whisk until smooth. Spread about 1 teaspoon of peanut butter mixture onto flat sides of 15 meringues, and top with remaining meringues.