Preheat oven to 350° F. Spray a 9x13 baking dish with non-stick spray and set aside.
In a large bowl, add all the "cake" ingredients (cake mix, one instant pudding mix, eggs, vanilla, chocolate milk, vegetable oil, and sour cream) and beat on medium speed until well combined.
15.25 ounce chocolate cake mix, 3.9 ounce instant chocolate pudding mix, 3 large eggs, 2 teaspoons vanilla, 1 cup chocolate milk, ½ cup vegetable oil, ½ cup sour cream
Pour into the 9x13 baking dish and bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.
Let cool for approximately 10-15 minutes then poke holes all over it using the end of a wooden spoon or something of similar size & shape.
For the hot fudge layer
Pour 1 cup of hot fudge sauce into a bowl and warm for approx. 20 seconds. Pour it over the cake and let it absorb into the holes, spreading with a spatula to evenly distribute. Place cake into the fridge to completely cool.
1 cup hot fudge sauce
For the chocolate pudding layer
Once the cake has cooled, prepare the pudding layer. In a medium bowl, add the instant chocolate pudding mix and 2 cups of milk. Whisk together and immediately pour over the cooled cake. Put the cake back in the fridge to set.
While the cake is setting, put the bowl of your stand mixer (or a metal mixing bowl) and whisk attachment into the freezer to get them really cold, for about 15 minutes.
To make the chocolate whipped cream
Remove the mixing bowl and whisk from the freezer. Add the heavy cream, cocoa powder, and powdered sugar to the chilled bowl and mix on medium-high until stiff peaks form. This can take up to 8-9 minutes.
2 cups heavy whipping cream, ¼ cup unsweetened cocoa powder, ½ cup powdered sugar
Remove the cooled cake from the fridge and top with the whipped cream, spreading it evenly with a spatula.
Drizzle with hot fudge sauce and top with marshmallow bits and mini chocolate chips.
hot fudge for drizzling, marshmallow bits, mini chocolate chips
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Notes
This recipe was originally written with International Delight Hot Chocolate, which has since been discontinued. It has been updated to include chocolate milk in place of the hot chocolate.Cool Whip or plain whipped cream can be used in place of the chocolate whipped cream.Store cake covered in the fridge for up to 3 days.