Not long ago I, too, attended the Wilton Cake Decorating class to brush up some. In class we used the following recipe for practice...on the practice board and later on our practice cake. The standard Wilton Icing follows. Since you will be just practicing you may wish to subistute water/milk for the pricy vanilla.

1/2 cup shortening
1/2 cup butter or margarine*
1 tsp vanilla*
4 cups sifted confectioners sugar (app 1 lb.)
2 Tbsp milk**

Cream butter and shortening with electric mixer. Add vanilla. Gradually add sugar, one cup at a time, beating well on medium speed. Scrape sides and bottom of bowl often. When all sugar has been mixed in, icing will appear dry. Add milk and beat at high speed until light and fluffy.

Keep icing covered with a damp cloth until you're ready to decorate/practice. For best result, keep icing bowl in refrigerator when not in use. Can refrigerate in airtight container for up to 3 weeks, rewhip before using.

Yields: 3 cups

*Substitute shortening and butter flavoring for pure white icing and stiffer consistency.

**Add 2 additional Tbsp milk to thin for icing cake.

Add more confectioners' sugar or chill icing to stiffen.