Heat oven to 350. Spray muffin tins w/ cooking spray. In lg bowl, mix cake as directed, spoon 1/2 way into muffin tins.
In another lg bowl, beat cream cheese and sugar until fluffy. Beat in egg. Stir in 1 cup chocolate chips. Drop 1 tsp of mix onto each muffin tin.
Bake as directed on cake box for muffins. In saucepan, over medium heat, bring cream to a boil. Place remaining chocolate chips in a bowl, pour cream over chocolate. Let cool 5 mins. Spoon chocolate sauce over each cupcake.