Peel and cut your onions in half. Then slice into thin slices.
Add the onions to your Instant pot with the oil and sauté until they are caramelized.
Add the broth to the onions.
Stir in the vinegar.
Then add the chicken.
Secure the lid and close the steam valve. Set to high pressure for 15 minutes for chicken breasts on the thinner side, and 20 minutes for chicken breasts on the thicker side. They are done when they have an internal temperature of at least 165°F. So be sure to check these with a meat thermometer when the cooking time is over. When done, you can do a quick release and remove the lid.
While the chicken cooks, make a slurry by mixing water and starch together until the starch is dissolved.
When the chicken is done, quickly stir the slurry into the hot broth.
Place some of the broth, onions, and chicken in a serving bowl, and sprinkle the grated cheese over the top.
Then ladle more hot broth over the cheese to help it melt. Let it sit for about 2-3 minutes for the cheese to fully melt. Then serve.
Video
Notes
Please note that the nutrition data given here is a ballpark figure. Exact data is not possible.