01 - Preheat the oven to 350°F. Grease a 9x13-inch baking pan thoroughly.
02 - Combine chocolate cake mix, eggs, water, and vegetable oil in a large bowl. Beat until smooth following package directions. Pour batter into the prepared pan and bake for 28 to 32 minutes, or until a toothpick inserted in the center emerges clean.
03 - Allow cake to cool for 10 to 15 minutes. Using the handle of a wooden spoon, poke holes across the surface, spacing them about 1 inch apart.
04 - Whisk instant vanilla pudding mix, cold milk, peppermint extract, and food coloring together in a medium bowl until thickened, about 2 minutes.
05 - Pour pudding evenly over the cooled cake, using a spatula to spread and encourage it into the holes.
06 - Cover and refrigerate the cake for at least 1 hour, or until pudding is set.
07 - Spread the thawed whipped topping evenly over the chilled cake.
08 - Sprinkle the surface with crushed peppermint candies and, if desired, chocolate shavings or mini chocolate chips. Slice and serve chilled.