01 - 
                Preheat the oven to 350°F. Spray a 9x13-inch baking dish with cooking spray.
              
              
              
                02 - 
                In a bowl, combine the cake mix, melted butter, and egg. Press the mixture evenly into the bottom of the prepared baking dish.
              
              
              
                03 - 
                Sprinkle the chocolate toffee bits evenly over the cake mix layer.
              
              
              
                04 - 
                Drizzle the sweetened condensed milk evenly over the toffee bits.
              
              
              
                05 - 
                Bake for 25-30 minutes, or until golden and set. Let the bars cool completely before cutting.