Prepare Choux Pastry: Preheat your oven to 230°C. Grease a 23 x 33 cm baking dish thoroughly to prevent sticking.
Cook Pastry Mixture: In a medium saucepan, combine the water, unsalted butter, and salt. Bring the mixture to a rolling boil over medium heat.
Incorporate Flour: Remove the saucepan from the heat. Add the all-purpose flour all at once. Beat vigorously by hand with a wooden spoon or use an electric mixer for about 2 minutes. The mixture should form a smooth ball of dough that pulls away from the sides of the pan.
Cool Pastry Dough: Transfer the dough to a mixing bowl. Allow it to rest and cool for 10 minutes. This step is crucial to prevent the eggs from cooking when added.
Add Eggs: Add the eggs one at a time. Beat thoroughly after each addition. The dough will look slippery at first but will become thick, smooth, and glossy as you continue mixing.
Final Dough Cooling: Let the finished dough cool for an additional 5 minutes. This helps it firm up slightly for spreading.
Shape and Bake Base: Spread the dough evenly into the greased baking dish. It does not need to be perfectly flat. Bake for 15 minutes at 230°C.
Release Steam and Continue Baking: Remove the pan from the oven. Use a knife to prick any large puffed areas about 15 times. This releases steam and prevents the pastry from collapsing. Reduce the oven temperature to 175°C and continue baking for 20 minutes, or until the pastry is golden brown and crisp.
Cool Pastry Shell: Remove the pan from the oven. Let the pastry shell cool completely in the pan, about 30 to 45 minutes. Do not rush this step.
Prepare Cream Layer: In a mixing bowl, beat the softened cream cheese until completely smooth. In a separate bowl, whisk the instant vanilla pudding with the milk until fully dissolved and slightly thickened. Gradually add the pudding mixture to the cream cheese, mixing gently at first. Then beat until the mixture is smooth and well combined.
Assemble Filling: Pour the cream filling evenly over the completely cooled pastry shell. Use a spatula to spread it gently.
Apply Whipped Topping: Spread the thawed whipped topping evenly over the cream layer. Be careful not to mix the two layers.
Finish and Chill: Drizzle the chocolate syrup over the surface in a decorative pattern. Refrigerate the dessert for at least one hour before serving to allow the layers to set.