01 - Preheat oven to 350°F and grease a 9x13-inch baking pan.
02 - In a large mixing bowl, combine cake mix, eggs, water, and vegetable oil. Mix with an electric mixer or whisk until batter is smooth and homogeneous.
03 - Pour batter into the prepared pan and bake for 28 to 32 minutes, or until a toothpick inserted in the center emerges clean.
04 - Allow cake to cool in the pan for 10 to 15 minutes.
05 - Use the handle of a wooden spoon to poke holes evenly across the cake surface, spacing holes about 1 inch apart.
06 - In a medium bowl, whisk together instant pudding mix, cold milk, peppermint extract, and food coloring until mixture has thickened, about 2 minutes.
07 - Pour pudding evenly over the cooled cake, using a spatula to gently spread and press pudding into the holes.
08 - Cover cake and refrigerate for at least 1 hour or until the pudding is fully set.
09 - Spread the thawed whipped topping evenly over the chilled cake.
10 - Sprinkle the surface with crushed peppermint candies and, if desired, chocolate shavings or mini chocolate chips.
11 - Slice the cake and serve chilled for optimal texture and flavor.