Prepare Spinach:

Thaw the frozen chopped spinach and squeeze out as much excess water as possible. You can use a clean kitchen towel or paper towels to do this.

Mix Ingredients:

In a large mixing bowl, combine the sour cream, mayonnaise, and ranch dressing mix. Stir until well combined.

Add the chopped green onions, chopped water chestnuts (if using), grated Parmesan cheese, and drained spinach. Mix thoroughly to ensure all ingredients are evenly distributed.

Season:

Taste the dip and add salt and freshly ground black pepper as needed. Mix well.

Chill:

Cover the bowl with plastic wrap and refrigerate for at least 1 hour to allow the flavors to meld together.

Serve:

Transfer the chilled ranch spinach dip to a serving bowl.

Serve with fresh vegetables, crackers, or chunks of bread for dipping.