You can use royal icing to make ... sugar, water, meringue powder and cream of tartar; beat on low speed just until combined. You can use either a hand mixer or a stand mixer to beat the icing ...

To make the icing, lightly whisk the egg whites adding the sugar at intervals ... desireable (for instance if you wish to store the cake for a long time or you want a really hard smooth set ...

Ready-made icing can be bought from most supermarkets, but it is easily made at home: the core ingredient, icing sugar ... temperature before using; you may want to lightly whip the icing again ...