Preheat oven to 350°F. Coat a 3-quart baking dish with cooking spray. Evenly sprinkle cake mix in the prepared dish and evenly sprinkle the pudding mix over the top.
In a medium bowl combine the milk, melted butter, and espresso powder (if using). Pour milk mixture over the cake mix mixture.
Use a whisk to just begin to combine the ingredients. (There will still be areas of dry mix. This is ok.)
Evenly top with chocolate chips. Bake 40 to 45 minutes or until set. Serve topped with whipped cream or ice cream, if desired.
