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