Step 1: Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan. Prepare and bake the chocolate cake mix according to the package instructions.
Step 2: While the cake is still hot from the oven, use the handle of a wooden spoon to poke holes across the entire surface of the cake, spaced about an inch apart.
Step 3: Slowly pour the entire can of sweetened condensed milk over the hot cake, making sure it seeps into the holes.
Step 4: Drizzle about 3/4 of the jar of caramel topping over the milk layer while the cake is still warm.
Step 5: Let the cake cool completely at room temperature, then transfer to the refrigerator for at least 30 minutes.
Step 6: Spread the whipped topping evenly over the cooled cake.
Step 7: Sprinkle the toffee bits generously over the top and drizzle with the remaining caramel sauce.
Step 8: Refrigerate for at least 4 hours, or preferably overnight, before serving to allow the flavors to meld.