Season both sides of the chuck roast with salt & pepper.
Set cooker to saute-high.
Add oil. Wait for 30 seconds.
Place the roast inside the cooker and sear both sides for about ~4-5 minutes per side. Remove the roast and place it on a plate/bowl.
Place the sliced (1) onion into the cooker; mix. Cook for 5-8 minutes or until mostly caramelized.
Add minced garlic and cook for 30-60 seconds or until fragrant.
Pour in dry sherry; using a wooden spoon, deglaze the bits and pieces on the bottom of the cooker.
Place the roast back into the cooker.
Add beef broth, worcestershire, soy sauce, thyme and bay leaves.
Place the lid on. Pressure cook on high for 55 minutes and natural release (approx. 55-60 minutes). Remove the lid. Press the cancel button. Note: test the meat for tenderness by stabing center with a fork. If the fork does not easily pierce through the meat, place lid back on and pressure cook for an additional 15 minutes with a natural release.
Remove the roast and place in a medium-large sized bowl, discard the bay leaves. Using 2 forks, shred the meat. Cover with aluminum foil until ready to eat.
Set cooker back to saute-high.
In a small bowl: combine cornstarch and water, mix until the cornstarch is fully dissolved.
Add corstarch mixture to IP. Simmer for 7-10 minutes or until desired consistency.
Season with salt & pepper to taste.