Cook 4 slices of bacon until crispy; drain, reserving 2 tablespoons drippings. Cook 1/4 cup chopped onion in reserved fat until tender. Add 1 to 2 tablespoons tarragon vinegar, 1/2 teaspoon salt, and dash of pepper. Pour over 2 cups hot cooked drained green beans. Crumble bacon on top. Serves 4.