Set your pressure cooker to sauté and set the time to 3 minutes. Add the Olive Oil (2 tablespoon), Onion (1), Carrot (2), and Celery (3 stalk) and stir.
Add in the Boneless, Skinless Chicken Breast (1). Season with Dried Thyme (1 teaspoon), Salt and Pepper (1 1/2 teaspoon), Dried Oregano (2 teaspoon), Garlic (2 clove) and mix.
Set the function to soup and time to 25 minutes on your cooker. Add in the Water (4 1/2 cup) and Chicken Base (5 1/2 tablespoon). Stir place the lid on your pressure cooker. Make sure your pressure valve is closed and let it cook.
Once done, release the pressure valve and once safe open the lid. Next shred the chicken. Season with Salt and Pepper (to taste).
Set your cooker back to sauté and add in the Heavy Cream (1 1/2 cup) and Milk (3/4 cup).
Whisk the Corn Starch (1/2 cup) and the Water (3/4 cup) in a bowl until fully combined.
Stir around and then add the water and cornstarch mixture. Stir again. Let it cook for another 5 minutes. Garnish with Fresh Parsley (to taste) and serve.