1 1/2 tablespoons Dijon mustard
2 tablespoons white wine vinegar
3/4 teaspoon kosher salt, plus more for the water
1/2 teaspoon freshly ground black pepper
1/3 cup extra-virgin olive oil
2 pounds green beans, trimmed
1 small fennel bulb, thinly sliced into half-moons (1 1/4 to 1 1/2 cups)
3/4 cup walnuts, toasted and coarsely chopped
1 4-ounce log fresh goat cheese, crumbled
In a medium bowl, whisk together the mustard, vinegar, salt, and pepper. Gradually add the oil and whisk until well combined; set aside.
Bring a large saucepan of salted water to a boil. Add the green beans and cook until just tender, 6 to 8 minutes. Drain, run under cold water to cool, and set aside until you’re ready to assemble the salad.
In a large bowl, combine the green beans, fennel, and walnuts.
Add the goat cheese and vinaigrette just before serving. Toss well and serve at room temperature or chilled.