Add oil to pressure cooker and set pot to saute. Set brisket inside and brown both sides. Turn pot off and remove meat. Pour in your broth and deglaze your pot (scraping stuck on pieces of meat off bottom).
Put meat back in with the fat side facing up. Add Worcestershire sauce, salt, garlic powder, rosemary and pepper on top of meat.
Close lid and steam valve. Set to 75 minutes (for this size brisket) and allow for a natural release when done.
Lift lid and allow to sit on cutting board for 10 minutes before slicing. If you want to make a thicker gravy, set pot to saute again. Take some of that hot liquid out into a bowl and whisk in 2 tbsp of cornstarch until smooth.
Pour this in when liquids are bubbling, stir consistently for 2 minutes then turn pot off and pour into gravy boat.