Preheat the oven to 350 degrees F. Place the paper baking cups into the cupcake molds.
Melt the chocolate in adding it to a small glass bowl set over a simmering saucepan of water and stirring until it melts. Stir in the milk to thin it out a bit.
Follow the package instructions and prepare the vanilla cake mix. Blend the cake mix with 3 eggs, 2/3 cup milk, and 1/2 cup oil. Pour 1/2 the mix in a separate bowl. Mix the melted chocolate into one of the bowls and stir for a couple of minutes, until you have reached a nice dark colored mix.
In each cupcake mold, use 1/2 vanilla and 1/2 chocolate mix, bake for 20 to 25 minutes.
Serve with a sprinkle of confectioners' sugar.
Two notes about my cupcake philosophy: More cupcakes, less icing! First. Kids need to know that cupcakes are good, regardless of the color of the icing... I cannot count how many kids I have seen digging their faces into their blue fluffed out cupcakes' icing, and actually never making it to the actual dough. I call it the icing tantrum...it happens almost immediately!!!