Potato and Green Bean Salad

700 gms new potatoes, cut into cubes
300 gms green beans, trimmed and halved crosswise
2 tablespoons balsamic vinegar
1 teaspoon seeded Dijon mustard
1/2 cup extra-virgin olive oil
1/2 teaspoon sugar
2 teaspoons chopped fresh lemon thyme, fresh lemon basil or plain thyme
zest from one lemon
salt and cracked black pepper to taste

1. In a large saucepan, place the potatoes, 2 teaspoons salt and enough water to cover by 1 inch. Bring to a simmer and cook until the potatoes are tender, 12 to 15 minutes.
2. Meanwhile, in a large bowl, combine the vinegar, sugar, mustard, lemon zest, salt and cracked pepper. Whisk in the olive oil until combined.
3. Steam the beans until tender but still bright green.
4. Toss the potatoes and beans with the dressing to coat. Season to taste with more salt and pepper. Serve warm or at room temperature.