For easy cleanup, line Crock Pot with parchment paper or slow cooker liner found near ziploc bags in the grocery store.
Prepare cake batter according to cake mix instructions on the box and pour into slow cooker.
Whisk milk and chocolate pudding mix until thoroughly combined. Pour over cake mix.
Empty the bag of chocolate chips over the cake and pudding.
Set Crock Pot to low for 3 hours.
Cake is done when top is just barely set and there are tunnels of bubbling chocolate sauce breaking the surface. May require more time based on temperature ands size of your Crock Pot.