01 - Preheat oven to 350°F. Grease a 9x13-inch baking pan thoroughly.
02 - Combine chocolate cake mix, eggs, water, and vegetable oil in a large mixing bowl. Blend until smooth following package directions.
03 - Pour batter into prepared pan and bake for 28 to 32 minutes, until a toothpick inserted in the center emerges clean.
04 - Allow cake to cool for 10 to 15 minutes before proceeding.
05 - Using the handle of a wooden spoon, poke holes evenly across the surface, spacing about 1 inch apart.
06 - In a separate bowl, whisk pudding mix, cold milk, peppermint extract, and food coloring, if using, until thickened, about 2 minutes.
07 - Immediately pour pudding over cake, gently spreading and pressing pudding into the holes with a spatula.
08 - Cover and refrigerate for at least 1 hour or until pudding is set.
09 - Spread thawed whipped topping evenly over chilled cake, smoothing gently.
10 - Sprinkle crushed peppermint candies and chocolate shavings or chips on top as desired.
11 - Slice and serve chilled for best results.