Preheat your oven to 350°F (175°C) and line a 9x9-inch baking pan with foil, leaving overhang for easy removal later. Lightly spray with cooking spray.

In a large mixing bowl, cream the unsalted butter until smooth and creamy, about 2-3 minutes.

Add the strawberry cake mix and egg to the creamed butter, mixing on low speed until fully combined.

Press two-thirds of the dough into the bottom of the prepared baking pan to form an even layer.

Sprinkle the white chocolate chips over the pressed dough and drizzle the sweetened condensed milk evenly over the top.

Crumble the remaining dough over the top of the mixture in small pieces.

Bake for 27-30 minutes until the edges are lightly golden and the center is slightly jiggly.

Allow the bars to cool for at least 2-3 hours, then lift out of the pan using the foil and slice into squares.