Stir shortening to soften. Gradually add sugar and cream together until light and fluffy (beat about 10 minutes at medium high speed on mixer, scraping bowl occasionally to guide batter into beaters.) Add vanilla extract. Sift flour with baking powder and salt; add to creamed mixture alternately with milk, beginning and ending with flour mixture; beat after each addition. Fold in egg whites. Bake in 2 paper-lined 9 x 1½-inch round pans in moderate oven at 375° F for 18 to 20 minutes. Cool. Frost.