To decorate, insert a basket weave decorating tip into a pastry bag and fill with the powdered sugar-white frosting mixture. Starting on the far left edge of the cake top, pipe a long stripe of icing straight across top of the cake. Cover the cake top with additional stripes, spaced 1/4 inch apart. Turn the cake 45 degrees; pipe additional stripes of icing across the original strips, spaced 1/4 inch apart. Pipe a border around top edge of the cake. Garnish the cake with fresh blueberries.