Preheat oven to 350F. Spray 2 sheetpans with nonstick spray. In a medium mixing bowl, cream together the butter, cream cheese, sugar and brown sugar. Beat in the vanilla. Into a small bowl, sift the flour, cocoa and salt through a mesh strainer and stir to combine. Blend the dry ingredients into the butter mixture. Stir in the chcoclate chips. Divide the dough into quarters and taking one-eight of a quarter roll it between the palms of two hands to form a ball and place it on a sheet pan. Repeat to form 32 dough nuggets. Using the bottom of a glass, press the nuggets into 2 inch rounds. Bake for 8 minutes until slightly puffed and very soft to the touch. Let cool on the pans for 1 minutes before transferring to racks to cool completely.