In a large pot, bring salted water to a rolling boil over medium-high heat. Carefully add the peeled and deveined large shrimp and cook for about 90 seconds if thawed or 3 minutes if frozen, until they are pink and opaque. Drain the shrimp in a colander and cool them completely by refrigerating for about 10-15 minutes.

While the shrimp chill, in a large mixing bowl, add finely chopped celery, mayonnaise, sour cream, fresh chives, chopped dill, fresh lemon juice, Dijon mustard, and a pinch of salt and pepper. Whisk until smooth and creamy.

Once the shrimp are chilled, gently fold them into the dressing. Add the thinly sliced English cucumber and mix well.

Cover the mixing bowl with plastic wrap or a lid and refrigerate the salad for at least 30 minutes.

After chilling, stir the salad gently, taste and adjust seasoning with salt, pepper, or lemon juice if necessary. Serve chilled in elegant bowls or on lettuce.