Chop or break up baking chocolate and place in a medium sized bowl. Heat the cream over low heat until it just simmers. Pour over the chocolate. Stir until melted and smooth. (If it’s having a hard time melting, place it in the microwave for about 15 seconds.) Chill chocolate mixture until hardened, at least 2 hours.
Preheat oven to 350 degrees. Line muffin tins with cupcake liners. (About 24)
Mix up cake batter according to the box directions. Fill each liner about 1/2 full of batter. (You don’t want to fill them as full as 2/3, or they will spill over. A little less than is called for on the box is good.)
Remove chocolate ganache from the refrigerator. Scoop 1 tablespoon balls (I used a cookie scoop) and place one ball in the center of each cupcake batter.
Bake 20-23 minutes, until a toothpick inserted in the side of the cupcake (not the center!) comes out clean. Cool for just a few minutes in the pans.
When ready to serve, remove the cupcakes from the pan and remove the liners. Turn upside down on a plate and sprinkle with powdered sugar.
These are best served warm. If they cool off, just heat them for a few seconds in the microwave to heat.