In a large bowl, whisk together mustard, lemon zest, and lemon juice. Slowly add in olive oil, whisking as you go, until vinaigrette emulsifies. Stir in shallot, garlic, and tarragon and set aside.
Bring a large saucepan of generously seasoned water to boil. Add haricot verts and cook until just tender, about 2-3 minutes. Drain and rinse under cold water to stop cooking. Pat beans try with kitchen towel.
Transfer them to the bowl with the vinaigrette and toss to coat. Season with sea salt and freshly ground black pepper to taste. Transfer to a serving dish and top with goat cheese and almonds.