Bring 4 qt. water and the 1/4 cup salt to a boil in a large saucepan. Meanwhile, in a medium mixing bowl, whisk together the shallot, vinegar, mustard, tarragon, the 1/4 tsp. salt, and black pepper. Slowly whisk in the olive oil.
Add the beans to the boiling water, stir once or twice to distribute them, and cook until tender throughout but not soft, 4 to 5 minutes, depending on the beans' size and freshness. Drain the beans in a colander. Put the beans in a serving bowl and toss with all the vinaigrette. Serve immediately.
nutrition information (per serving):
based on six servings;
Photo: Scott Phillips