Combine oats, butter and boiling water. Set aside for 20 minutes. Beate together the eggs , sugars and vanilla. Sift dry ingredients and add, 13x 9 inch baking pan. Bake at 350 F for 30 to 35 minutes. Or until an inserted toothpick comes out clean. Cool for a few minutes. Then combine frosting ingredients, spread on cake and place under a broiler for one minute or until frosting begins to bubble.