Thoroughly wash the tongue under cold running water
Place the tongue on the Instant Pot rack, add 1 1/2 cups of water or bone broth, close the lid and the pressure valve, and turn on the Instant Pot on "pressure cook" (high) for 1 hour
Let the Instant Pot naturally release the pressure for about 15 minutes and carefully open the lid. Take the tongue out and place it on a cutting board. Once the tongue is not too hot to touch anymore (but still warm), remove the skin with your fingers or with the help of a knife. You should be able to easily peel the skin off the meat. If some of the white harder pieces of skin are still on the meat, scrape them off using a knife
Cut the tongue meat into chunksSave about 2/3 cup of the tongue cooking liquid, and discard the rest (or save it to add extra flavor to other recipes!)
Finely chop the onion, and peel and cut the potatoes and carrots into chunks
Turn the Instant Pot on "sauté" and add the butter and clove of garlic (optional)
Once the butter is melted, add the chopped onions and let them sauté for a few minutes stirring often with a wooden spatula
Add the chunked tongue meat, potatoes and carrots and season with sea salt and a few leaves of fresh, chopped parsley. Add about 2/3 cup of the tongue cooking liquid (or bone broth or water) and stir to combine everything together
Turn off the "sauté" function, place the Instant Pot lid on with the valve closed, and turn the Instant Pot on "pressure cook" (high) for 20 minutes
At the end of the 20 minutes, release the pressure and safely open the Instant Pot lidIf the stew if too runny, turn back the Instant Pot "sauté" function and let the stew reduce for a few minutes, stirring frequently
Serve warm and garnish with fresh parsley, if desired