-Bring 1 inch of water to a boil in a large pot fitted with a steamer basket.
-Fill a large bowl with ice water; set it aside
-Place the green beans, stem ends trimmed, in the steamer basket. Cover and steam until the beans are crisp-tender, 5-8 minutes
Plunge the beans in the ice water to stop the cooking
-When the beans are cool, drain and pat them dry with paper towels. Transfer the beans to a large bowl
In a small bowl or jar, whisk or shake the olive oil, vinegar, Dijon mustard, sugar, salt & pepper until they are combined
Pour the vinaigrette over the beans, toss to coat, then serve