Step 1: In a large mixing bowl, combine the strawberry flavored gelatin mix with 1 cup of boiling water. Stir continuously for about 2 minutes, or until the gelatin is completely dissolved.
Step 2: Add 1/2 cup of cold water to the gelatin mixture and stir well. Place the bowl in the refrigerator for 15-20 minutes, allowing it to partially set and thicken slightly. It should be viscous but not firm.
Step 3: While the gelatin chills, beat the softened cream cheese and powdered sugar together in a separate medium bowl until the mixture is smooth and free of lumps.
Step 4: Gently fold the cream cheese mixture into the partially set gelatin until well combined and smooth.
Step 5: Carefully fold in the thawed whipped topping, diced fresh strawberries, and mini marshmallows until all ingredients are evenly distributed throughout the fluffy mixture.
Step 6: Transfer the entire mixture into a large serving bowl. Cover the bowl with plastic wrap.
Step 7: Refrigerate for at least 2-4 hours, or until the fluff salad is completely set and thoroughly chilled. Garnish with a few extra fresh strawberries or marshmallows just before serving, if desired.