Cake: Sift flour once, measure, add baking powder, and sift together three times. Cream shortening thoroughly, add sugar gradually, and cream together until light and fluffy. Add flour, alternately with milk, a small amount at a time. Beat after each addition until smooth. Add vanilla. Fold in egg whites.
Bake in two greased 9 inch layer pans in a 375 F oven 25 to 30 minutes. Put layers together with Orange Filling and cover top and sides of cake with Seven Minute Frosting. Decorate with mandarin orange sections.
Filling: Combine ingredients in order given. Cook in a double boiler ten minutes, stirring constantly. Cool.
Frosting: Put egg whites, sugar, water, corn syrup, and salt in top of double boiler and mix thoroughly. Place over rapidly boiling water and beat constantly with a rotary egg beater until the mixture will hold a peak (about seven minutes). Remove from hot water, add vanilla and marshmallows and beat until cool and thick enough to spread.
12 Servings.