Preheat your oven to 325°F. While waiting for the oven to heat up, grease a baking dish with butter or non-stick spray to prevent sticking. If you prefer easy removal, line the baking dish with parchment paper, leaving an overhang for easy lifting once baked.

In a large bowl, combine the egg, softened butter, and yellow cake mix. Stir until the ingredients are well incorporated, and you achieve a dry dough-like mixture. This mixture will serve as the base of your bars and provide a sturdy foundation for the gooey filling.

Transfer the mixture into the greased baking dish. Use your hands or the back of a spoon to evenly press the dough into the bottom of the dish. Ensure it covers the entire base in an even layer to create a uniform crust.

In another large bowl, beat the softened cream cheese until smooth and creamy. Add the vanilla essence and eggs, mixing until well combined. The mixture should be silky and free of lumps.

Set aside ¼ of the powdered sugar in a small bowl. Slowly mix the remaining powdered sugar into the filling mixture, stirring constantly to prevent clumps. Mixing gradually ensures a smooth, lump-free batter that blends seamlessly into the creamy filling.

Pour the prepared filling over the crust, spreading it evenly with a spatula. Bake in the preheated oven for 40-50 minutes until the top is golden brown. The center will still be slightly jiggly, which is fine as it will firm up while cooling.

Once baked, allow the bars to cool completely before slicing. If the bars appear puffy, don’t worry—they will settle as they cool. Sprinkle the reserved powdered sugar over the top for a decorative finish. Cut into squares and serve at room temperature.