Peel and cut the potatoes into cubes. Boil them in salted boiling water for 20' - 25'. Leave them to cool.
Mix in the blender yogurt, mayonnaise, cheese and vinegar. Pour the mixture into a large salad bowl, add some salt and plenty of pepper.
Drain the potatoes, and pour them into the bowl. Add the onion and the chopped dill. Stir well and serve.