Soak poppy seeds in 1/2 cup water for 2 hours. Drain off water. Prepare a 9-inch square pan or two 8-inch layer pans.
Cream shortening and sugar. Add poppy seeds. Sift together flour, baking powder and salt. Add alternately with 1 cup water. Fold in egg whites.
Pour into prepared pans. Bake at 350 degrees for 30 to 35 minutes. Cool. Use custard filling between layers and frost with chocolate frosting.