Put sauté function on your pressure cooker and add about two tablespoons of oil
Season the oxtail with salt and black pepper on all sides.
In the hot oil, sear the oxtail in batches. Brown all sides of the oxtail and set aside.
Once all pieces are seared, add onions and cook until translucent.
Add garlic and ginger and cook for 30 seconds or until fragrant.
Add tomato paste and cook for about 2 minutes.
Add worcestershire sauce if using. Then add about a half cup of chicken stock to deglaze the pan. Use a wooden spoon to scrape all the browned bits. For a pressure cookers, its important all bits are scrapped off to avoid a burn spot.
Once deglazed, add back the seared oxtail pieces, the rest of the chicken stock , bay leaves, rosemary and time.
Close the lid of the pressure cooker, ensure the knob is on the sealing mark. Put the pressure cook function and set a timer for 45 to 50 minutes.
Once the timer goes off, allow the pressure cooker to release pressure naturally for 15 minutes.
After the 15 minutes, release the residual pressure manually and once the valve drops, you can safely open the pressure cooker.
Remove the oxtail pieces, remove the herbs and discard. For the oxtail pieces, shred the meat to add back to the sauce.
With the shredded meat back in the sauce, put back the saute function and thickened the sauce if needed.
If using a corn starch slurry, in a small bowl mix corn starch and colder and stir it into the sauce. The slurry thickens the sauce and makes it look glossy.
If using the beurre maine, knead the softened butter with the flour, then add it to the sauce. Stir to cook.
Turn off the pressure cooker and add chopped fresh parsley and grated parmesan cheese if using.