1. Heat a large pan over medium high heat. Add in the oil and swirl around. Add in the beef stew meat in one layer and let brown (about 3-4 minutes) and then turn over to other side and brown. 
2. Sprinkle in the salt, pepper and flour and stir. 
3. Add in the diced onion, tomato paste, Worcestershire, vinegar and mushrooms and toss well until onion is soft (about 3 minutes). Turn off heat.
4. Turn Instant Pot to sauté setting. Add in the beef broth and bring it to a boil. Once broth is boiling add in the meat mixture but don’t stir. Turn off sauté setting.
5. Immediately cover Instant Pot and lock lid into place. Make sure valve is set to sealing. Set the manual/pressure cook button to 15 minutes. 
6. When time is up let pot sit for 15 minutes and then move valve to venting. Remove the lid.
7. Stir the cornstarch and heavy cream/milk together until smooth. Turn Instant Pot to saute and add the mixture into the pot. The sauce will thicken quickly.
8. Salt and pepper to taste. Serve beef, mushrooms and sauce over mashed potatoes, buttered egg noodles or rice.

To make in the slow cooker: complete steps 1-3 above and then transfer mixture to a slow cooker and stir in 2 ½ cups of broth. Cover and cook on low for 6 hours. Stir the cornstarch and heavy cream/milk together until smooth. Stir the mixture into the slow cooker and cook on high without the lid for about 10-15 minutes until thickened. 

To make in the oven: complete steps 1-3 on the stove top in a dutch oven. Stir in 2 ½ cups broth and deglaze. Cover and cook in the oven at 300° F for 2 hours. Stir in cream and serve.