01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan.
02 - In a large mixing bowl, combine chocolate cake mix, eggs, water, and vegetable oil. Blend with an electric mixer or whisk until smooth and fully incorporated.
03 - Pour the batter into the prepared pan. Bake for 28–32 minutes, or until a toothpick inserted in the center comes out clean.
04 - Allow cake to cool for 10–15 minutes. Using the handle of a wooden spoon, poke holes evenly across the cake surface, spaced about 1 inch apart.
05 - In a medium bowl, whisk instant vanilla pudding mix, cold milk, peppermint extract, and food coloring (if using) for about 2 minutes until thickened.
06 - Immediately pour the pudding evenly over the cooled cake, gently spreading and pressing the pudding into the holes using a spatula.
07 - Cover and refrigerate for at least 1 hour, or until fully set.
08 - Once chilled, spread the thawed whipped topping evenly over the cake surface.
09 - Sprinkle with crushed peppermint candies and chocolate shavings or mini chips if desired.
10 - Slice and serve chilled for optimal flavor and texture.