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 following package directions until batter is smooth.
03 - Pour batter into prepared pan and bake for 28 to 32 minutes, or until a toothpick inserted into the center emerges clean.
04 - Cool cake for 10 to 15 minutes. Using the handle of a wooden spoon, poke holes across the surface, approximately 1 inch apart.
05 - In a medium bowl, whisk together vanilla pudding mix, cold milk, peppermint extract, and food coloring until thickened, about 2 minutes.
06 - Pour pudding evenly over the cake, spreading and pressing gently with a spatula to fill the holes.
07 - Cover pan and refrigerate for at least 1 hour or until pudding is set.
08 - Spread thawed whipped topping evenly over chilled cake.
09 - Sprinkle with crushed peppermint candies and chocolate shavings or chips if desired.
10 - Cut cake into squares and serve chilled.