You first want to hit "Saute" on your Instant Pot. Move to the normal setting and then begin melting the butter in the Instant Pot.
Add in your pork shoulder and sear for about four minutes on each side. You want the entire pork shoulder to be nice and brown. Hit "Cancel" on the Instant Pot.
Grab a small bowl, and add in the garlic, salt, soy sauce, broth, and brown sugar. Pour this mixture over the pork shoulder.
Close the lid on the Instant Pot and seal the valve.
Press "Manual" on the Instant Pot, move to high pressure. Set the cooking timer for 90 minutes.
Once that timer is up, click "Cancel" and allow for a natural release of pressure.
You will be able to remove the lid and take out the pork shoulder. Shred up the meat and pour about a cup of the liquid from the Instant Pot over the meat. You can discard the rest of the juices.