• In a sizable mixing bowl, combine the softened cream cheese with the pistachio Jell-O instant pudding mix. Utilize a mixer to achieve a light and fluffy texture.
• Gradually incorporate the crushed pineapple, ensuring to include its juice.
• Integrate the miniature marshmallows into the mixture, ensuring even distribution.
• Delicately fold in either the Cool Whip or the previously whipped heavy cream.
• Transfer the resulting mixture into the prepared pie crust. It is imperative to refrigerate the concoction for a minimum of two hours to ensure it sets properly.

For the optional toppings:

• In a separate mixing bowl, whip the heavy cream, incrementally adding the powdered sugar, until you achieve stiff peaks.
• Using a piping bag, adorn the top of the refrigerated pie with the whipped cream.
• For the finishing touch, garnish with chopped pistachios and maraschino cherries as desired.