Family Tested & Approved
chilled heavy whipping cream
Whisk powdered sugar, milk and cream of tartar in large bowl until smooth. Cover and refrigerate until well chilled, about 1 hour. (Can be prepared 4 hours ahead.)
Using electric mixer, gradually beat cream into chilled mixture. Continue beating until stiff peaks form. Place cake on platter. Spread top and sides of cake with icing. Slice into wedges and serve.