Bring the butter, syrup, sugar and liquorice powder to boil in a small saucepan. Let the mixture cool down to room temperature; then mix in the eggs. Combine the baking soda and the flour, and add the mixture to the dough. Let the dough rest in the refrigerator overnight.
Roll the dough out into a 3-mm rectangle between two sheets of SAGA Baking Paper. Remove the top sheet and use a cutter to cut out the cookies. Remove the excess dough so that only the gingerbread cookies are left on the lower sheet. Bake at 200°C until they are a beautiful brown colour.
Prepare the royal icing by placing one egg white into a bowl. Add 250 ml of icing sugar and one teaspoon of lemon juice and mix until smooth. If necessary, add more icing sugar or lemon juice; the mixture should be a fairly thick paste.
Place the royal icing in the piping bag and pipe an outline on the edges of the gingerbread cookies. You can also decorate the gingerbread cookies with a lace pattern. Let the royal icing dry for about an hour.
Prepare a thinner royal icing from two egg whites, 350 ml of icing sugar and 2 teaspoons of lemon juice. This royal icing should be runny. Pipe the royal icing carefully inside the dried outlines. You can spread it towards the edges with a toothpick. Let dry for about 24 hours.
Stamp the gingerbread cookies by patting or brushing liquid food colouring on a clean rubber stamp. Wipe off any excess colour with a piece of household towel and carefully stamp the gingerbread cookies. Let dry well before packaging.