Preheat oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan or line with parchment paper.

In a large mixing bowl, combine cake mix, eggs, vanilla, and cherry pie filling. Mix until well combined—batter will be thick.

Fold in milk and semi-sweet chocolate chips.

Pour batter into the prepared baking pan and spread evenly.

Bake for 30–35 minutes or until a toothpick inserted in the center comes out clean.

While the cake is baking, prepare the ganache: heat heavy cream in a small saucepan over medium heat until it just begins to simmer (do not boil).

Remove from heat and pour over dark chocolate chips in a bowl. Let sit for 2–3 minutes, then stir until smooth. Stir in butter if using.

Once cake is baked and slightly cooled, pour ganache over the top and spread evenly.

Let cake cool completely before slicing and serving.