Grease a 9x13 baking dish with nonstick cooking spray.
Sprinkle the dry cake mix and instant chocolate pudding mix into the bottom of the greased pan.
Add the butter and milk to the pan and lightly mix with a whisk.
Sprinkle the mixture with chocolate chips and M&Ms.
Bake for 40 to 45 minutes or until cooked throughout (it should be gooey, but not runny).
Allow to cool slightly before serving with a scoop of vanilla ice cream.
Video
Notes
The cake should be gooey, but not runny.You may use dark chocolate baking chips instead of the semi-sweet, if desired.You may let this chocolate dump cake sit out overnight, if needed.