Place the potatoes in a saucepan, cover with cold water, bring to a boil, cover and reduce the heat to low. Cook until the potatoes are just tender, about 20 minutes. Drain and quarter the potatoes, taking care to keep the skins on.

Place potatoes in a bowl, season lightly with salt and pepper and gently toss with 2 T vinegar and 1 T oil. Set aside to cool.

Mix remaining vinegar with the mustard until well blended.

Beat in the oil. Pour over the cooled potatoes and gently mix.

Add scallions and dill, season to taste with salt and pepper.