Measure oats into mixing bowl. Add boiling water; stir and cool. cream both sugars, butter and shortening. Add eggs and vanilla; beat very well. Sift dry ingredients together. Add oatmeal mixture and sifted dry ingredients alternately to creamed mixture. Pour into greased and floured 9x13x2 inch pan. Bake 30-40 minutes in preheated 350 degree oven. Have frosting ready; spread on hot cake and place under broiler for a few minutes to brown. Watch carefully. Frosting: Mix frosting ingredients together and blend well. This cake was a second place winner at the Del Mar fair. Jo Anne Merrill