Line a half-sheet baking sheet (10x15-inch) with parchment paper or spray with nonstick cooking spray.
Using an electric hand mixer or stand mixer, add the cake mix, eggs, melted butter, and boiling water into a large mixing bowl and mix until smooth and combined. Use a spatula to scrape down the sides and bottom of the bowl, as needed.
Gently stir in ¾ cups of mini chocolate chips.
Then pour the batter into the prepared baking sheet. Spread out into an even layer.
Gently tap the baking sheet on the counter to release any air bubbles.
Evenly sprinkle on the remaining ¼ cup of mini chocolate chips.
Place in the oven and bake for 12-16 minutes or until a toothpick comes out clean and the top of the cake bounces back when gently tapped.
Remove the cake from the oven and allow it to cool completely before making the frosting (about 1 hour).
When ready to frost the cake: In a medium mixing bowl, using an electric mixer, mix together the melted butter and cocoa powder until smooth.
Slowly beat in 1 ½ cups of the powdered sugar until incorporated. Be sure to scrape down the sides and bottom of the bowl with a spatula to incorporate all of the ingredients.
Beat in 2 Tablespoons of heavy cream and then repeat with the remaining powdered sugar and heavy cream (alternating the two) until the frosting reaches the consistency of a light, fluffy frosting. If necessary, add additional heavy cream (a little at a time.)
Spread the frosting into a smooth layer onto the cooled cake.
When ready to serve, cut it into squares and enjoy! Optional: top each slice with a scoop of vanilla ice cream.
Notes
Please refer to my FAQ’s (Frequently Asked Questions) and ingredient list above for other substitutions or for the answers to the most common questions.
This cake makes anywhere between 25-35 servings depending on the size that you cut your cake slices.