Combine all ingredients in a large mixing bowl. Beat with electric mixer until well blended and smooth. Frosting will be very thick and at first look like it needs more water. Frosting may be thinned by adding small quantities (1 teaspoon at a time) of ice water, but should be quite thick if used for decorating. Frosts and decorates one 2-layer 9 inch cake or one 9 x 13 inch sheet cake.