Preheat the oven to 375°. Line a 12-cup muffin cups with muffin papers.
In a mixing bowl, combine the neufchatel cheese, sugar, egg, and vanilla. Beat until smooth. Set aside.
In a large mixing bowl combine the milk, oil, sour cream, and eggs. Whisk until well blended.
In a bowl, whisk together the muffin mix and cocoa powder. Add this to the liquid ingredients. Add the chocolate chips. Fold just until combined.
Divide the batter among the muffin cups. It's okay if the cups overflow. Divide the cream cheese mixture among the cups.
Bake for 25 to 30 minutes or until a tester comes out clean.
Cool the baked muffins on a wire rack.
Notes
Nutritional values are approximate and are based on 1 muffin. Use within 3 days or freeze for longer storage.To freeze muffins unbaked: Assemble the recipe as directed. Instead of baking, slide the pan into the freezer for several hours until the muffins are frozen solid. Remove the frozen muffin “pucks” from the pan and store them in an airtight container in the freezer. To bake, replace the frozen muffins into a muffin tin and bake, adding five minutes to the baking time if needed.To freeze baked muffins: Bake the muffins according to the recipe and cool completely on the rack. Place in an airtight container or ziptop bag and store in the freezer, for up to 2 months.Variations: Other baking chips such as cinnamon or butterscotch can also be used in lieu of chocolate.