Preheat oven to 350°F. Line 9×13-inch pan with parchment paper.
Mix cake mix, melted butter, and egg until crumbly.
Press ⅔ of mixture into prepared pan.
Pour condensed milk over base layer.
Sprinkle with toffee bits and chocolate chips.
Crumble remaining cake mixture over top.
Bake 25-30 minutes until golden.
Cool completely before cutting into bars.
