Preheat the oven according to the cake mix directions (usually around 350°F/175°C).
Grease a 9×13-inch baking pan and prepare the cake according to the package instructions.
Bake until golden and a toothpick comes out clean, usually 25ā30 minutes. Let cool for 15 minutes.
2ļøā£ Poke Holes in the Cake
Once the cake has cooled for 15 minutes, use a wooden spoon handle to poke holes all over the surface of the cake. Make sure the holes are evenly spaced.
3ļøā£ Add the Vanilla Pudding Layer
In a medium bowl, whisk together the two boxes of instant vanilla pudding and 4 cups of cold milk until smooth and thickened.
Pour the pudding over the cake, allowing it to fill the holes. Smooth the top with a spatula.
Chill the cake in the refrigerator for 1 hour to let the pudding set.
4ļøā£ Make the Chocolate Ganache
In a microwave-safe bowl, combine the chocolate chips and heavy cream.
Microwave in 30-second bursts, stirring in between, until smooth and glossy (about 1ā1.5 minutes total).
Let the ganache cool slightly before pouring over the cake.
5ļøā£ Top the Cake
Pour the chocolate ganache over the chilled cake, spreading it evenly with a spatula to cover the entire surface.
Refrigerate the cake for another 30 minutes to let the ganache firm up before serving.