To make the icing, beat the egg white with an electric mixer until soft peaks form in a mixing bowl. Add the lemon juice. Then, start adding the icing sugar gradually, spoon by spoon. Keep beating until stiff peaks form.
Transfer the mixture to a piping bag and decorate your cookies.
• If you do not have a piping bag, use snap lock bags for piping decorations onto Gingerbreads. • To easily fill a snap lock bag, put it into a tall glass and fold edges over the rim of the glass. • Spoon icing mixture into the snap lock bag and push the mixture into one corner of the bag. • Close the bag or secure the top of the bag by twisting it so the mixture does not come out of the other end as you pipe. • Make a very small snip in the corner of the snap lock bag with a pair of scissors and start piping icing onto cooled Gingerbread (Lebkuchen).