Fill a large saucepan with water and bring it to a rolling boil. Season the water generously with salt before adding the couscous. Let it cook for 8 to 10 minutes or until the grains are tender but still retain a slight chew. Drain well and set aside.

While the couscous is cooking, prepare the dressing. In a spacious mixing bowl, whisk together the olive oil, Dijon mustard, honey, lemon zest, lemon juice, 1/2 teaspoon of salt, and 1/4 teaspoon of freshly ground black pepper. Once the couscous has been drained, add it to the bowl with the dressing and stir until the grains are evenly coated.

Gently fold in the diced cucumber, chopped tomato, fresh herbs, toasted walnuts, and raisins. Mix well to ensure even distribution of ingredients. Taste and adjust the seasoning with additional salt and pepper if needed.

Serve immediately while warm, or cover and refrigerate for about an hour to allow the flavors to meld. If preparing in advance, store covered in the refrigerator for up to four hours. For longer storage, keep the tomatoes and walnuts separate until ready to serve to maintain their freshness and texture.