Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 9x13-inch baking dish.

Combine milk and non-instant pudding mix in a saucepan. Cook over medium heat, stirring constantly, until pudding is thickened. Remove the pan from heat and stir in cake mix until batter is smooth. Pour into the prepared baking dish. Sprinkle with chocolate chips.

Bake in the preheated oven until a toothpick inserted into the center of cake comes out clean, 20 to 30 minutes.