Lay FROZEN chicken breasts on the bottom of and 8 quart Instant Pot. (See NotePour salsa and sprinkle brown sugar over the chicken.
Secure the Instant Pot lid and turn the top nozzle to the [Sealing] position. Set the [Manual] or [Pressure Cook] setting to high for 20 minutes.
It will take approximately 10 minutes for the Instant Pot to gain pressure before cooking time begins. After the cooking is complete, let the chicken sit and naturally release pressure for 10 minutes before venting the remaining pressure with the top nozzle.
To shred the chicken, you can remove the chicken to a cookie sheet and hack at it with a metal spatula or forks. OR, use the whisking attachments in your countertop mixer (I use the Boscand put an entire breast into the mixer. Pulse three or four times and your chicken will be evenly and perfectly shredded.
This makes about 25 half-cup servings of chicken.