01 - Preheat oven to 350°F and grease a 9x13-inch baking pan.
02 - In a large mixing bowl, combine chocolate cake mix, eggs, water, and vegetable oil. Beat according to package directions until batter is smooth.
03 - Pour batter into prepared pan and bake for 28 to 32 minutes or until a toothpick inserted in the center comes out clean.
04 - Allow cake to cool in the pan for 10 to 15 minutes.
05 - Using the handle of a wooden spoon, poke holes evenly over the cake surface, approximately 1 inch apart.
06 - In a medium bowl, whisk together instant pudding mix, cold milk, peppermint extract, and food coloring until thickened, about 2 minutes.
07 - Pour the pudding mixture evenly over the cake while it is still slightly warm, spreading gently and pressing it into the holes with a spatula.
08 - Cover and refrigerate for at least 1 hour until pudding is set.
09 - Spread thawed whipped topping evenly over the chilled cake.
10 - Sprinkle crushed peppermint candies and chocolate shavings or chips over whipped topping. Slice and serve cake chilled.