01 - Preheat oven to 350°F. Lightly grease a 9x13-inch baking pan.
02 - Combine chocolate cake mix, eggs, water, and oil in a large mixing bowl. Blend with an electric mixer or whisk until batter is smooth and well incorporated.
03 - Pour batter into prepared pan. Bake for 28 to 32 minutes, or until a toothpick inserted in the center comes out clean.
04 - Let cake cool in the pan for 10 to 15 minutes.
05 - Using the handle of a wooden spoon, poke holes across the entire cake surface, spacing approximately 1 inch apart.
06 - In a medium bowl, whisk instant vanilla pudding mix, cold milk, peppermint extract, and food coloring together until thickened, about 2 minutes.
07 - Evenly pour prepared pudding over cooled cake, spreading with a spatula and pressing gently to fill holes.
08 - Cover cake and refrigerate for at least 1 hour or until pudding is set.
09 - Spread thawed whipped topping evenly over chilled cake.
10 - Scatter crushed peppermint candies and optional chocolate shavings or mini chips across the top.
11 - Cut into portions and serve cold.