Bake the cupcakes according to the package directions. Let them cool completely.
Prepare the vanilla pudding with cold milk and chill until firm.
Cut a small hole in the center of each cupcake and fill with pudding.
Heat the cream until just simmering, pour it over the chopped chocolate, add butter and corn syrup, and stir until smooth.
Spoon or dip the tops of the cupcakes into the chocolate glaze. Let the glaze set before serving.