Prepare an ice bath by filling a large bowl with ice cubes and cold water; set aside.
In a large mixing bowl, whisk together the extra-virgin olive oil, red wine vinegar, Dijon mustard, shallot, kosher salt, and black pepper until emulsified. Stir in the fresh parsley and fresh tarragon.
Bring a large pot of water to a rolling boil. Add the green beans and cook until bright green and crisp-tender, 3–5 minutes.
Drain immediately and transfer to the ice bath to stop the cooking, 1–2 minutes. Drain well and pat dry with towels so the dressing clings.
Add the cooled beans to the bowl with the vinaigrette and toss to coat evenly. Let stand 5–10 minutes to absorb flavors, then serve at room temperature or lightly chilled.