How to Make It
In a bowl, toss the walnuts with 2 teaspoons of the vinegar and let stand for 10 minutes.
In another bowl, whisk the mustard with the remaining 2 teaspoons of vinegar and the olive oil and season with salt and pepper.
Arrange the tomatoes on a platter; season with salt. Add the celery and leaves, nuts and cheese. Drizzle with the dressing and serve.