Melt the milk chocolate and let cool, but not harden. You'll need to keep an eye on it. You don't want it to get hard, but it needs to be cool enough that it won't melt the rest of the filling
Whip the butter and the cream cheese together until combined and fluffy
Add the powdered sugar, cream, vanilla, and salt. Beat until light and fluffy
Turn the mixer on low/medium low and slowly pour in the milk chocolate
Once the chocolate is added, turn the mixer up to high and beat until it's very light and fluffy. It should be whipped up like mousse.
Add in the Oreos (or Glutinos) and mix until combined.
Put into a piping bag and pipe onto the cooled macaron shells
Refrigerate them until the filling is set. We're going to dip them next, so you want to make sure the filling is hard enough to hold the top shell in place.