1. Boil potatoes, until tender.
2. Peel and cut into cubes and place in a bowl.
3. Combine mustard, salt, pepper and lemon zest in small bowl.
4. Add juice and whisk until blended. Slowly whisk in olive oil.
5. Pour dressing mixture over the potatoes and toss gently.
6. Season with more salt and pepper, if desired and serve.