Preheat oven to 350 degrees F (175 C)

Prepare a 9 x 13 inch cake pan with butter and flour.

With a mixer on low speed, beat the cake mix, chocolate milk, canola oil, eggs, and espresso powder together in a large bowl.

Mix until the dry ingredients are moistened.

Increase the mixer speed to medium and continue to beat for 2 more minutes.

Pour chocolate mixture into the prepared pan.

Bake for 30 minutes or until a toothpick inserted comes out clean.

Remove the cake from the oven and allow it to cool in the pan until is is no longer hot to the touch, but is warm.

While the cake is warm, poke holes all over the cake with a fork.

Whisk the sweetened condensed milk, half-and-half, evaporated milk, and 3 Tbsp. cocoa powder together in a bowl until the cocoa is mostly incorporated into the liquid.

Allow the cake to cool completely.

Pour this milk mixture evenly over the cooled cake. (You may even want to make more to pour over the cake to make it extra moist -- totally up to you!)

Allow the liquid to soak into the cake.

Sift the powders sugar and cocoa powder together in a bowl.

Beat the heavy whipping cream in a stand-up mixer on medium speed for 1 minute.

While continuing to mix, add the sugar and cocoa powder mixture to the cream in 2 batches, allowing the first to incorporate before adding the second.

Increase mixer speed to medium-high and beat until soft peaks form and the cream is thickened and spreadable.

Add the coffee liqueur by gently folding it into the whipped cream mixture.

Spread chocolate whipped cream on the cake to serve.

Notes

I adapted this recipe by amping up the coffee flavor by adding the Tia Maria coffee liqueur, the original (without liqueur): AllRecipes.com