Step 1: Lightly grease a 9x13 inch baking dish.
Step 2: In a medium bowl, combine the graham cracker crumbs, granulated sugar, and melted butter. Mix well until crumbs are evenly moistened. Press the mixture firmly and evenly into the bottom of the prepared dish. Chill in the refrigerator for 15-20 minutes.
Step 3: In a large bowl, beat the softened cream cheese with an electric mixer until light and fluffy. Gradually add the powdered sugar and vanilla extract, continuing to beat until smooth and well combined.
Step 4: Gently fold in half (about 6 ounces or 2 cups) of the thawed whipped topping into the cream cheese mixture until just combined.
Step 5: Evenly spread the cream cheese mixture over the chilled graham cracker crust. Return the dish to the refrigerator and chill for at least 30 minutes.
Step 6: In a heatproof bowl, combine the two packages of strawberry gelatin with 2 cups of boiling water. Whisk continuously for at least 2 minutes, or until the gelatin powder is completely dissolved. Add 1 cup of cold water and stir well. Allow the jello mixture to cool down to room temperature (about 10-15 minutes).
Step 7: Carefully pour the cooled strawberry jello mixture over the chilled cream cheese layer. Place the dish back into the refrigerator and chill for at least 2-4 hours, or until the jello is completely set and firm.
Step 8: Once the jello layer is fully set, spread the remaining thawed whipped topping evenly over the strawberry jello.
Step 9: Garnish with fresh sliced strawberries, if desired. Chill for an additional 30 minutes before serving for optimal firmness. For best slicing, dip your knife in hot water and wipe clean between each cut.