01 - Preheat oven to 350°F. Lightly grease a 9x13-inch baking pan to prevent sticking.
02 - In a large bowl, combine chocolate cake mix, eggs, water, and oil. Mix with an electric mixer or hand whisk following package guidelines until smooth and well blended.
03 - Pour batter into prepared pan and bake for 28–32 minutes, or until a toothpick inserted in the center emerges clean.
04 - Let the cake cool for 10–15 minutes. Use the handle of a wooden spoon to create holes over the cake surface, spacing each about 1 inch apart.
05 - In a medium bowl, whisk instant pudding mix, cold milk, peppermint extract, and food coloring until thickened, approximately 2 minutes.
06 - Gently pour pudding over the cooled cake, using a spatula to spread and press pudding into the holes for even absorption.
07 - Cover and refrigerate cake for at least 1 hour, ensuring the pudding sets before adding toppings.
08 - Evenly spread thawed whipped topping across the entire surface of the chilled cake.
09 - Sprinkle crushed peppermint candies and chocolate shavings or mini chocolate chips, if desired, over the topping for added flavor and decoration.
10 - Slice chilled cake and serve. For best texture, keep cake refrigerated until ready to enjoy.