Most modern versions contains potato flour or some other starch, but thicker soup can also be achieved by adding more rose hip. I tried these proportions:
100 g dried rose hip, no seeds
1000 ml water
100 ml honey
Boil rose hip in 900 ml water for about 20 minutes. Mix. Depending on how good your mixer is and how much body you want to your soup you might wish to strain it as well. I did, and then I added the honey solved in the rest of the water.
I found it much too sweet and will use less honey next time. I have no idea what I was thinking adding a large chunk of honey rather than adding a little and tasting it. I will also consider using ground rose hip instead of whole pieces.