Start by preheating your oven to 350°F (175°C). While it heats, take a 9×13-inch baking pan and either lightly grease it or line it with parchment paper so the cake won’t stick.

Grab a large mixing bowl. Add in the chocolate cake mix, white sugar, and melted butter. Crack in the eggs, pour in the milk, and add the cherry pie filling. Stir everything together until it’s fully combined and you have a thick, smooth batter. Once that’s done, fold in 1 cup of semisweet chocolate chips.

Pour the batter into your prepared baking pan and spread it out evenly. Smooth the top with a spatula. Place the pan in the oven and bake for 30 to 35 minutes. You’ll know it’s done when a toothpick poked into the center comes out clean.

Take the cake out of the oven and let it sit in the pan on a wire rack for about 20 minutes. It should still be a little warm, but not hot, before you frost it.

While the cake cools, put a medium saucepan on the stove over medium heat. Add the butter, sugar, and milk. Stir constantly until the sugar fully dissolves and the mixture starts to simmer. Once it begins to bubble, turn the heat down and let it cook for another 2 to 3 minutes, stirring often.

Take the saucepan off the heat and stir in the chocolate chips right away. Keep stirring until they’re completely melted and the frosting is smooth and glossy.

Pour the warm frosting over the mostly cooled cake. Use a spatula to spread it out evenly across the top. Let it sit at room temperature until the frosting firms up. Once it’s set, slice and serve.