In the bowl of a stand mixer, cream the butter and cream cheese together until you have a smooth consistency.
Add in the cocoa and mix until combined.
Incorporate the flour, salt and brown sugar until smooth. (may be a little lumpy but will smoot out once other ingredients are added)
Add the milk and vanilla.
Then add the confectioners sugar one cup at a time.
Whip the dip until it is all blended, smooth and creamy.
Pour into your serving bowl and garnish with chocolate chips if desired.