01 -
Preheat oven to 350°F. Line a 9×9 inch baking pan with foil. Spray with cooking spray and set aside.
02 -
Beat butter with a mixer until soft and fluffy. Add in cake mix, egg, lime juice, and zest, and continue beating until combined.
03 -
Press about two-thirds of the cake mixture onto the bottom of the foil-lined baking pan.
04 -
Sprinkle white chocolate chips over the top. Drizzle the sweetened condensed milk over the top of the chocolate.
05 -
Crumble the remaining cake mixture over the top of the sweetened condensed milk, trying to spread it out as much as possible. Press lightly.
06 -
Bake for 29-32 minutes, or until edges start to brown.
07 -
Let bars cool completely before cutting. Top with additional lime zest if desired.
08 -
Store in an airtight container for up to a week.