Preheat oven according to package directions. In a large bowl, prepare the chocolate cake mix as directed. Grease a 9×13 baking pan, pour in the batter, and bake until a toothpick inserted in the center comes out clean.
In a medium microwave-safe bowl, combine the sweetened condensed milk and ½ cup Kahlua. Microwave for about 1 minute, or until the mixture just begins to boil. Carefully remove from the microwave.
Place the chocolate chips in a medium bowl and pour the warm condensed milk mixture over the top. Stir until smooth and the chocolate is fully melted.
Use the handle of a wooden spoon to poke holes all over the cake. Pour the chocolate Kahlua mixture evenly over the cake, allowing it to seep into the holes. Refrigerate until completely cooled.
Once the cake is fully chilled, prepare the whipped topping by combining all ingredients (except the chocolate chips) in a mixing bowl. Using an electric mixer, beat on high speed until stiff peaks form.
Spread the whipped topping evenly over the cake. Sprinkle with additional chocolate chips or drizzle with chocolate sauce, if desired. Slice and enjoy!