Lemon balm, 2 kg sugar, 2 lit water, 30g citric acid, 4 lemons
Dilute the sugar with water, bring to boil, add the citric acid and pour over the lemon balm. Let it stand for 3 days next to a window. Strain through a muslin cloth. Bring to boil and fill in sterilised hot bottles, turn bottles for a moment.
You can dilute it with still or sparkling water, use it to make a cocktail or add it to deserts.