In the bowl of a stand mixer, cream together cream cheese and butter until smooth.
With the mixer on low speed, add powdered sugar a little at a time until fully incorporated.
Add 2 tablespoons of milk and mix until smooth, then add cocoa powder, flour, brown sugar, and vanilla. Beat until smooth and fully combined. {If dip is too thick at this point, add another tablespoon of milk and mix until desired consistency is reached.}
Pour mixture into a small dish. Carefully spread marshmallow fluff over top of the cream cheese mixture.
Sprinkle chopped walnuts over marshmallow fluff. Set aside.
Heat heavy cream for about 45 seconds in a microwave safe cup. (Keep an eye on it, it tends to bubble over.) Add butter and chocolate chips and let sit for about 2 minutes.
Whisk cream & chocolate until silky and thickened. Pour over top of walnuts.
Serve dip with pretzels, fruit, or cookies.