Preheat oven to 350ºF. Coat regular-sized muffin molds with cooking spray.
Beat together light butter and sugar. Beat in pumpkin, apple sauce, egg, vanilla, and milk.
In a separate bowl, whisk together flour, baking powder, baking soda, pumpkin pie spice, and salt.
Gently fold in flour mixture to wet mixture, being sure not to over mix. Gently fold in 4 tbsp of chocolate chips, reserving 2 tbsp to sprinkle on top.
Divide batter among muffin pans. Sprinkle remaining chocolate chips evenly over the top of each muffin.
Bake until a toothpick inserted into center comes out clean, about 22-26 minutes. Let cool in muffin mold for 5 minutes if using silicon. If using an aluminum pan, let cool for 15 minutes before. removing to cool completely.