- In a saucepan of boiling salted water, cook the beans until al dente, about 2 to 3 minutes. Plunge the beans into ice water to stop the cooking. Drain and set aside.
- In a salad bowl, combine the vinegar, mustard and walnut oil. Season with salt and pepper. Add the celery and green beans and mix well. Adjust the seasoning.
- Sprinkle with the chopped nuts and oregano.