Make cake batter according to box directions and pour 1/2 cup of batter into greased cups of a large muffin pan. If your pan has six cups, bake the cakes in 2 batches of 4 cakes each. Bake for 30-40 minutes, or until a toothpick stuck into the centre of one cake comes out clean. Turn all the cakes out of the pan and let them cool.
The cakes will be served upside down, so you may have to slice a bit of the domed top off the cakes to help them lay flat when inverted. A serrated knife works best for this. After you've flipped over all the cooled cakes, use a sharp paring knife to cut out a 1.5 inch diameter cylindrical chunk in the centre of the bottom (now the top) of each cake. The hole should be about 1.5 inches deep. After slicing straight down into the cake in a circle, scoop out the chunk of cake with a teaspoon and discard the piece. Now you have a secret compartment to conceal the hot fudge payload.
Spoon about 2 tablespoons of fudge into each of the holes you've made in the cakes, then store the cakes in a sealed container in the fridge.
When you are ready to serve, heat one cake at a time in the microwave for 40 to 45 seconds on high, or until you see the fudge begin to bubble. Remove the cake from the microwave and let it rest for 30 seconds or so, then place a scoop of vanilla ice cream on top of the cake. Pour a coating of Magic Shell chocolate topping over the ice cream and serve.