Cake: Comine and soak a minimum of 3 hours the poppy seeds and milk. When ready to bake cake, cream together until light, butter and sugar. Sift together cake flour, salt and baking powder. Add sifted ingredients to creamed mixture, alternately with poppy seed milk mixture, mixing well. Quickly beat until stiff egg whites and fold into mixture. Pour into 2 9-inch pans greased and floured. Bake at 350 degrees for 30 minutes or until lightly browned and springy. Cool cake in pans 10 minutes on racks. Turn out and cool completely. Frosting: Combine in saucepan sugar, cornstarch. Beat together then add, mixing until smooth, egg yolks and milk. Add lastly broken pecans and cook very slowly, stirring frequently to prevent burning until thick like filling, 20 to 25 minutes. Remove and add vanilla. When cool spread frosting between layers and on top of poppy seed cake.