Sift together flour, baking powder and salt twice.
Beat egg whites until foamy. Add 6 tblsp. of sugar, 1 tblsp. at a time, beating until mixture stands in soft peaks.
Cream shortening; add 1⅔ c. sugar gradually. Cream until light and fluffy.
Add flour, alternately with milk, a small amount at a time, beating after each addition until smooth. Add egg whites and flavorings; beat thoroughly (about 1 minute).
Grease or line pans with waxed paper. Batter fills two 9" square pans or one 13x9x2" pan.
Bake in moderate oven (350°). Cakes in square pans take 30 to 40 minutes, in oblong pans, 35 to 50 minutes.
Cool cakes on racks 10 minutes. Loosen from sides of pan, turn out and remove paper. Turn right side up to cool. To keep from drying, cover or wrap as soon as cooled. Make recipe 5 times; assemble cake.
You will have one and one-half 9" square cakes left over to sample. To make cake to serve 40 you will have one-half 9" cake left over for a sampler. You can make the Formal Cake and the small edition with packaged white cake mix. Layers will not be so thick unless you add more batter—enough to fill the pans ½ to ⅔ full.