Mix together your ground beef, packet of french onion soup mix, 1 tbsp worchestershire sauce, bread crumbs, and 1 egg. (skip if using frozen meatballs). Make into medium size meatballs.
Spray the inside of your Instant Pot with non stick spray and add a bit of olive oil inside. Set to saute, low.
Add your meatballs and diced onions to your pot and cook until the outsides are browned (if using frozen meatballs skip this step). Turn pot OFF. Take meatballs out and add 1/2 your can of beef broth to deglaze your pot.
Mix together all your other ingredients in another bowl and use a whisk to make sure all lumps are gone.
Pour your cream mixture into the pot and put meatballs back in. Put your lid on, close your steam valve.
Push the pressure high button on your Instant Pot for 3 minutes for homemade meatballs. If using defrosted previously frozen meatballs cook for only 3 minutes as well. If using frozen meatballs need 5 minutes (for small frozen, larger may take longer).
Once it's done and beeps do a quick release.
Check meatballs to ensure they're cooked thru. Remove the meatballs from the pot.
Set Instant Pot to saute low again.
Add remaining 2-3 tbsp. of cornstarch and whisk into liquid in pot.
Allow to bubble and thicken, add more cornstarch if desired.