Trim the stem ends from the green beans and, if using, halve or quarter the small red potatoes so pieces are roughly the same size as the beans. Slice the shallot very thinly and halve the cherry tomatoes. If using, quarter the hard-cooked eggs. Chop the fresh herbs and set all prepared ingredients aside.

Cook potatoes (if using)

Place the potatoes in a pot, cover with cold salted water (about 1 inch above potatoes), bring to a boil, then reduce to a simmer. Cook until just tender when pierced with a fork, about 10–12 minutes depending on size. Drain and set aside to keep warm or cool slightly if serving chilled.

Blanch beans

Bring a large pot of salted water to a rolling boil. Add the trimmed green beans and cook until bright green and just tender-crisp, 2–4 minutes depending on thickness. Meanwhile, prepare a bowl of ice water. When beans are done, use a slotted spoon to transfer them immediately to the ice bath to stop cooking. Leave for 2–3 minutes, then drain thoroughly and pat dry or spin in a salad spinner.

Make dressing

In a small bowl or a jar with a lid, combine the white wine vinegar, Dijon mustard, lemon juice, minced garlic, and salt. Whisk or shake until the salt dissolves. Gradually whisk in the olive oil until the dressing is emulsified. Taste and adjust seasoning with more salt or pepper as needed. Add freshly ground black pepper and stir to combine.

Assemble salad

In a large bowl, combine the blanched green beans, cooked potatoes (if using), halved cherry tomatoes, and thinly sliced shallot. Pour about two-thirds of the dressing over the vegetables and gently toss to coat, taking care not to break the beans or tomatoes.

Let the salad sit for 10–15 minutes at room temperature to allow flavors to meld (or chill for 30 minutes if serving cold). Taste and add more dressing if desired.

Just before serving, fold in the chopped fresh herbs and arrange the quartered hard-cooked eggs on top if using. Finish with an extra drizzle of olive oil or a light sprinkle of sea salt and freshly ground black pepper to taste.