In a small bowl, whisk together the broth, Worcestershire sauce, soy sauce, sugar, onion powder, and salt until the sugar has dissolved.
Place the beef into the bottom of the instant pot. Pour the broth mixture over the roast.
Lock the lid, set the pressure level to high, and manually set the cook timer to 50 minutes.
When the roast is finished cooking, allow the pressure cooker to perform a natural release, which could take about 20-25 minutes.
Using two forks, shred the meat and mix it with the sauce, coating completely.
Heat a large skillet over medium heat and butter the cut side of each of your sandwich buns.
Set the buns, cut side down, in the pan, and allow to toast for 1-2 minutes until nice and golden brown.
Remove the toasted buns from the pan and use a slotted spoon to fill with the shredded beef.