1. Preparing the Equipment and Ingredients

Before starting, preheat the oven to 350°F (177°C). Line a 9×13 inch baking pan with parchment paper or generously coat it with non-stick cooking spray. This will make it easier to remove and cut the bars once they have cooled.

2. Making the Crust and Crumble Topping

In a large mixing bowl, combine the softened butter, granulated sugar, and brown sugar. Use a hand mixer or a wooden spoon to cream these ingredients together until they become light and fluffy. This step is essential for creating a tender crust.

Next, add the baking soda and salt, stirring until evenly distributed. Gradually incorporate the all-purpose flour and quick-cooking oats, mixing until the dough becomes crumbly.

Take half of this mixture and press it firmly into the bottom of the prepared baking pan, ensuring an even layer. Bake the crust for about 13 minutes or until it is just set and slightly golden.

3. Preparing the Cream Cheese Filling

While the crust is baking, start on the filling. In a separate large bowl, beat the softened cream cheese until it is completely smooth, ensuring there are no lumps.

Gradually add the sweetened condensed milk, whisking continuously until fully incorporated. This will create a rich and creamy consistency. Stir in the vanilla extract and egg yolk, mixing until the ingredients are well combined.

4. Assembling the Bars

Remove the partially baked crust from the oven. Immediately pour the cream cheese mixture over the warm base, using a spatula to spread it evenly. This will help create a uniform layer.

Scatter the blueberries evenly over the cream cheese layer, ensuring they are distributed across the surface. This ensures every bite contains bursts of blueberry flavor.

Finally, sprinkle the remaining oat mixture over the top of the blueberries, pressing it down lightly to create a crumbly, textured top layer.

5. Final Baking

Return the pan to the oven and bake for an additional 20 to 25 minutes. The bars are ready when the edges are golden brown, and the topping is slightly firm to the touch. Avoid overbaking, as this can cause the filling to dry out.

6. Cooling and Cutting

Once the bars are finished baking, remove the pan from the oven and allow it to cool completely on a wire rack. This is an important step, as cutting the bars while they are still warm can cause them to fall apart.

Once cooled, lift the bars out of the pan using the edges of the parchment paper. Transfer them to a cutting board and slice them into the desired sizes.