Add the chestnuts to a large bowl (large enough to cover them with a lot of water.
Boil water and then pour it over the chestnuts. Let sit for 15 minutes.
Remove any chestnuts that have floated to the very top of the bowl (as those may be rotten). Then place the chestnuts on a cutting board flat side down and cut an "x" in the top of the chestnut. Cut just enough to cut through the shell and not too far into the chestnut.
Add the chestnuts to the air fryer. Air fry at 400 degrees F for 7-10 minutes, shaking after 5 minutes and checking at the 7 minute mark for doneness.
Add your air fried chestnuts to a kitchen towel and wrap. After 3-4 minutes, remove and add to a bowl or paper cones and sprinkle with salt. Peel and enjoy.
Notes
Don't skip soaking the chestnuts in water! It may seem unncessary, but it's an important step to cooking them properly.
When making the "x" in the chestnuts, try not to cut too deep. You want to cut through the shell, but not through too much of the chestnut (though I admit, sometimes I cut into a little too much of the chestnut, but they still come out fine).
Wrapping the chestnuts in a kitchen towel after they come out of the air fryer for a few minutes will make the chestnuts even easier to peel! So it's not completely necessary, but I usually do it.
This recipe will make enough to serve four people. If you're making it for 1 or 2 people, definitely cut the amounts in half.