Place the stainless steel inner pot inside the Instant Pot® and press Saute. Add the avocado oil and sauté the onion, garlic, red tomato, and green tomatoes. Once golden brown, add the dried chiles, cook until lightly brown, and add the water, spices, and seasoning.
Close and lock the Instant Pot® lid, making sure the steam release handle is turned to Sealing. Press Pressure Cook and set time to 5 Minutes.
When the time is up, release the steam (by turning the handle). Once all the pressure has been released, open the lid, blend everything, taste for seasoning, and set aside.
Season the meat with salt and pepper.
On a sheet of parchment paper, place a bottom layer of the sauce, a chunk of meat on top, coat with more sauce, and add the potatoes. Close the paper and tie with the twine, securing with several knots to keep it from opening. Repeat for all the chunks of meat.
Place the rack inside the Instant Pot® bowl, add 2 cups water and place the mixiotes one on top of the other, without going over the max line.
Close and lock the Instant Pot® lid, making sure the steam release handle is turned to Sealing. Press Steam and set time to 40 Minutes.
Serve the mixiotes: carefully cut the twine or floss, open up, and eat hot.