Do you mean you built a double thick wall as in 2x4 framing twice? And now the door jamb is not thick enough? If this is what you mean I had the same problem when I put OSB on the walls and then drywalled over top of the osb. Just take some 1x stock and strip it to fit the gap. Caulk or use wood putty and paint it. Nobody will eve know.
I believe this is referring to the gap between two communicating doors that are installed for sound isolation in a "room-within-a-room" scenario, where the inner and outer door frames should not touch each other to keep the inner and outer walls isolated from each other.
I've heard two schools of thought on this. One is to leave a 1/4" or so gap between the doors so that air can move into the wall structure so that pressure does not build up when the doors close. The other is to seal the gap with flexible material, such as a gasket or backer rod and caulking to prevent musty smells from within the walls from getting out into the living spaces.
"That gap in between doors is simply filled with a bead of sealant and covered with a piece of wood trim. You can attach the trim piece on one side of the gap only. That's about as decoupled as is practical "