Put the vinegar and water in a saucepan, then stir in sugar, salt and vegetable stock powder (I always use my homemade stock powder, recipe from the CK database). Bring to the boil while stirring, then remove from heat.
In a separate bowl, mix the sour cream with the yogurt, mustard and honey. Stir this cream into the hot vinegar broth and finally stir in the oil. Pour into a bottle and keep in a cool place. I always have this dressing in the fridge and use it for every salad.