Start by preheating your oven to 350°F (175°C). This step is crucial because an evenly heated oven ensures your bars bake uniformly.

Use a 9x13 inch baking dish and grease it lightly with butter or cooking spray. This prevents the bars from sticking and allows for easy removal.

In a large mixing bowl, combine the softened cream cheese, melted butter, and vanilla extract. Whisk these until smooth, creating a rich, creamy base. The texture should be silky and fully blended. Next, add in the sour cream. This ingredient adds tanginess that balances the sweetness.

Crack in the eggs one at a time. Mix thoroughly after each addition. This ensures each egg fully integrates, providing structure and stability to your mixture. Your batter should look luscious and silky.

Gradually mix in the granulated sugar. This step transforms your mixture, adding that essential sweetness. Make sure to blend until no granules remain, allowing the ingredients to shine together.

Gently fold in the yellow cake mix. Avoid over-mixing; you want it combined but not overworked. The cake mix is what gives these bars their signature texture.

Pour the mixture into your prepared baking dish. Spread it evenly, ensuring every corner is filled. Place it in your preheated oven and allow it to bake for 30 to 35 minutes. The edges should turn golden, but a toothpick inserted in the center may come out slightly wet.

Once baked, remove the dish from the oven. Allow it to fully cool before slicing. This could take a few hours but trust me—you want to let the flavors settle!