Preheat air fryer 360 F for 5 minutes. In a small bowl, mix contents of pickling package with mustard and apple cider vinegar. Place corn beef on a large piece of aluminum foil, big enough to wrap corn beef.
Spread 2/3 of mustard mixture over meat, top and sides. Fold foil around corn beef and place in air fryer basket. Cook at 360 degrees for 1 hour.
Carefully pull back foil, spread remaining mustard mixture on top of corn beef, recover, and cook for another 40 minutes.
Pull back foil, cook at 400 F for 5 minutes to crisp the top of the meat, if desired. Lift out of foil and on to a cutting board. Slice against the grain and serve with cabbage.
Video
Notes
Internal Temperature of Fall-Apart Corned Beef
You need it to reach 145F for food safety reasons but with this cut you need it to cook longer to break down the connective tissues. To reach a fall-apart texture it needs to be 160-180F so I tend to aim for 170F, lift out, cover with foil, allow to rest for 10 minutes covered (it will rise another 5 degrees during that time) and then slice against the grain on a cutting board.