In large bowl, combine 2/3 cup water and meringue powder; whip with electric mixer at high speed until peaks form. Add 4 cups sugar, one cup at a time, beating at low speed after each addition. Add remaining 8 cups sugar and 3 tablespoons water, shortening and corn syrup in 3 additions, blending well after each. Add salt and flavorings; beat at low speed until smooth. Keep bowl covered with a damp cloth until ready to use. For best results, keep icing bowl in refrigerator when not in use. Refrigerated in an airtight
container, this icing can be stored 2 weeks. Rewhip before using.
For thin (spreading) consistency icing, add up to 4 more tablespoons each water and corn syrup.
NOTE: Changes in Wilton's traditional recipes have been made due to Trans Fat Free Shortening replacing Hydrogenated Shortening.