Thoroughly drain the thawed spinach to remove all moisture—wrap it in a clean kitchen towel and squeeze until nearly dry. Transfer the spinach to a medium mixing bowl, gently breaking apart any clumps for even distribution.

Add sour cream and mayonnaise to the spinach. Mix until fully combined and smooth. Sprinkle in the Knorr Vegetable Recipe Mix, folding until the seasoning is evenly incorporated with no dry spots. For a subtle flavor boost, add ¼ teaspoon freshly ground black pepper.

Fold in chopped water chestnuts and green onions, ensuring even texture throughout. Transfer to a serving bowl, cover with plastic wrap, and refrigerate for at least 2 hours (overnight for best flavor). Let sit at room temperature for 15 minutes before serving.