Prepare cake according to box instructions in a 9x13" pan.
Right before cake comes out of the oven prepare the pudding by adding the chocolate pudding mix, milk, and peppermint extract in a large bowl. Whisk to combine (2 minutes). Add 1 cup of the peppermint crunch baking chips and stir together.
After cake comes out of the oven use the back of a wooden spoon to poke holes all over the cake.
Pour the pudding mix over the warm cake and use a rubber spatula to spread it evenly over the cake, making sure to get the pudding into the holes.
Refrigerate until chilled completely (about 1 hour).
Top evenly with Cool Whip and sprinkle with the remaining 1 cup of Peppermint Chips.