Heat your pressure cooker by hitting the Saute function and waiting until Instant Pot reads, Hot.
Add 1 tablespoon olive oil to the inner pan of the pressure cooker.
Season chicken breasts generously with salt and pepper on each side.
Sear chicken breasts 2 to 3 at a time for 1-2 minutes per side. Remove browned chicken breasts to plate.
Add in a dash more oil to the inner pan of Instant Pot if no oil remains after searing chicken. Add in mushrooms, dried thyme, and garlic to the Instant pot, saute for 1-2, or until the garlic begins to toast.
Add in the Marsala wine and deglaze the pan, by scraping up any browned bits of chicken off the bottom of the pan. Turn the heat OFF on the Instant Pot.
Add in beef broth or mushroom broth. Return browned chicken back to Instant Pot and submerge in sauce.
Place the lid on the pressure cooker, turn the valve to sealed, and set Chicken Marsala to cook on high pressure for 6 minutes for thin chicken breasts, 7 minutes for average size chicken breasts, and 8 minutes for larger chicken breasts.
Once cook time has elapsed, let the pressure release naturally for 10 minutes (this helps to keep the chicken from getting tough). Then release any remaining pressure.
Remove chicken breasts to serving platter.
Turn off Instant Pot and then turn back to Saute.
Whisk together cornstarch with 2 tablespoons water.
Whisk in a cornstarch slurry and stir constantly, until sauce is bubbly and thickened--about 3-4 minutes. Add in the butter if desiring a richer sauce.
Pour sauce over chicken cutlets and serve.
You can use boneless skinless chicken thighs in place of chicken breasts if desired. Cook time will remain the same.
To determine cook time. Use 6 minutes for chicken breasts/thighs that are between 6 and 8 ounces each and 7 minutes for 8-9 ounce chicken breasts/thighs, and 8 minutes for 9-10 ounce chicken breasts/thighs (or really thick chicken). Add 1 minute of cook time if you skip the step of searing the chicken.
In place sliced baby bella mushrooms, feel free to use sliced shitake mushrooms OR 1-ounce of rehydrated dried wild mushrooms.
Be sure to use a good quality dry Marsala Wine for this Chicken Marsala recipe--not a cooking marsala wine you find in the spice aisle of your grocery store.
I use beef broth to add extra flavor to the Chicken Marsala sauce, but you can use chicken stock if you'd like.
Feel free to finish your Chicken Marsala with a tablespoon or two of butter to make the sauce even richer--just remember it will no longer be a Dairy-Free recipe.
Leftovers can be stored in the refrigerator for up to 3 days.