Dice the onion and fry lightly in the rapeseed oil. Roughly chop the dill and fry briefly. Deglaze with a little water and let it steep a little. In a measuring cup, mix the cream with the water, the granulated stock and the flour with a whisk. Then add to the dill / onions in the pan and bring to the boil. Add 1 sprig of lemon balm to the sauce and let it steep while the sauce is thickening. Stir a little every now and then so that the result is a nice, delicate consistency. At the end, take the branch out again.