Combine cooking oil and sugar. Beat until smooth. Add egg yolks and beat well. Add dry ingredients which have been sifted together. Stir in potatoes, nuts and vanilla, beat well. Beat egg whites until stiff. Fold into mixture. Bake in 3 greased and floured 20 cm layer pans at 180ºC . for 25-30 min. Cool and frost. FROSTING: Combine milk, sugar, oleo, egg yolks and vanilla in sauce pan. Heat until boiling. Add coconut and continue to cook 3 to 5 min. or until mixture thickens. Remove from fire, and place saucepan in container of ice and beat with wooden spoon until spreading consistency.