Heat the oven to 350°F and line two 12-cup muffin pans with paper liners. Prepare the chocolate cake batter according to the package directions, using the 3 eggs and 1/3 cup vegetable oil listed here, and do not mix the cherry filling into the batter.

Divide the batter among the 24 liners, filling each about two-thirds full. Bake for 18–22 minutes, until the tops spring back lightly and a toothpick inserted into the cake portion comes out clean.

Cool the cupcakes in the pans for about 5 minutes, then transfer them to a wire rack. Let them cool completely before coring, filling, or frosting.

Chill the cherry pie filling briefly so it becomes thicker and easier to handle. Remove a small cone from the center of each fully cooled cupcake with a paring knife or cupcake corer, then spoon approximately 1 teaspoon of filling into each cavity.

Beat the softened butter until smooth for the frosting. Gradually add the cocoa powder and confectioners’ sugar, alternating with the milk, then beat in the vanilla until the frosting is light and spreadable.

Pipe or spread the chocolate frosting over each filled cupcake. Finish with a reserved cherry or maraschino cherry and chocolate shavings or mini chocolate chips, if desired.