01 -
Heat the oven to 350°F. Grease a 9x13-inch baking pan with nonstick spray or butter.
02 -
Prepare the cake mix with the eggs, water, and oil according to the package directions. Spread in the pan and bake until the center springs back and a tester comes out clean, usually 28-35 minutes.
03 -
Let the cake rest for 5 minutes. Use the handle of a wooden spoon to poke holes about 1 inch apart across the warm cake, going almost to the bottom.
04 -
Slowly pour the sweetened condensed milk over the cake, aiming for the holes. Let it absorb for 2 minutes, then spoon the warmed caramel topping evenly over the surface.
05 -
Cool the cake completely at room temperature. Cover and refrigerate for at least 2 hours, or overnight for cleaner slices.
06 -
Spread the thawed whipped topping over the cold cake. Sprinkle with chopped candy, drizzle with a little extra caramel if using, and add a tiny pinch of flaky salt if desired.
07 -
Cut cold with a warm, wiped knife. Store leftovers covered in the refrigerator.