Preheat the oven to 350 degrees F.
In a large bowl, combine the flour, cocoa powder, baking soda, and salt. Set aside.
In the bowl of a stand mixer or another large bowl, cream the butter and the sugars until smooth and fluffy, about 3 minutes.
Add the eggs and mix well.
Add the milk and vanilla.
Add the flour mixture a little bit at a time and beat thoroughly.
Stir in the peanut butter cups and chocolate chips.
Drop by rounded spoonfuls onto ungreased cookie sheets, leaving several inches in between to allow for spreading.
Bake for 10-12 minutes.
Cool on sheets for 1 minute, then remove to racks and allow to cool completely.
