Place all of the ingredients in the bowl of an electric mixer. Beat slowly until all of the ingredients are blended. Then, beat at high speed until icing forms stiff peaks, about 5 minutes. Add more sugar if the icing is not stiff enough, or a few drops of water if it is too stiff. Use immediately, or cover the bowl with a damp cloth to prevent drying when not in use. Allow at least twenty-four hours for royal icing decorations to dry at room temperature.