1. Preheat oven to 350 degrees F.
2. In a large bowl, add cake mix, frosting mix, egg yolk and oil. Mix well.
3. In a separate bowl, whip the egg whites until peaks form.
4. Gently fold the egg whites into the chocolate mixture.
5. Pour into cupcake tins. Be sure to fill only halfway. Insert one square from the chocolate bar into the batter for each cupcake.
6. Bake for 10-14 minutes.
7. Cool for 10 minutes and gently peel cupcake wrapper off. Flip upside down and sprinkle with confectioner's sugar. Enjoy!