Beat cream cheese, sugar, powdered sugar, and peanut butter in a large bowl with a mixer until blended. Gently stir in cool whip until blended.
Spoon mixture into crust. Turn the broiler on low. Sprinkle marshmallows over the top of the pie. Broil marshmallows just until they are toasty brown. You will want to watch this the whole time it is in the oven because it only takes a minute for the marshmallows to brown. Remove from oven. Refrigerate at least 4 hours or until firm. Just before serving, drizzle hot fudge on top. Keep leftovers in the refrigerator.