Begin by bringing a large pot of salted water to a rolling boil. Add the fusilli pasta and cook according to package instructions, typically around 8-10 minutes, until al dente. Drain the pasta and rinse under cold water.

While the pasta cools, take the frozen chopped spinach and place it in a mesh strainer. Allow it to thaw completely and press down firmly with paper towels to squeeze out excess moisture.

In a large mixing bowl, combine the cooled fusilli pasta, well-drained spinach, sour cream, mayonnaise, garlic powder, onion powder, pepper, sea salt, and dried parsley. Mix gently until everything is evenly coated.

Incorporate the sliced water chestnuts into the pasta salad mixture, folding them in gently with a spatula.

Cover the bowl with plastic wrap and refrigerate for at least 30 minutes before serving.

After chilling, stir the salad, taste for seasoning, and serve cold.