Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish with cooking spray or butter.
In a large mixing bowl, combine the chocolate cake mix, chocolate pudding mix, water, vegetable oil, eggs, and vanilla extract. Mix until well combined and smooth, about 2-3 minutes.
Fold in the semi-sweet chocolate chips gently until evenly distributed.
Pour the batter into the prepared baking dish, spreading it evenly.
Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
While the cake is baking, prepare the glaze by whisking together the powdered sugar and milk in a small bowl until smooth.
Once the cake is done, remove it from the oven and let it cool for about 10 minutes. Drizzle the glaze over the warm cake.
Serve warm or at room temperature, topped with whipped cream and chocolate shavings or sprinkles if desired.