Place the chicken breasts, chicken stock, chopped onions, and garlic into the liner of your Instant Pot.
Secure the lid and make sure the venting knob is in the Sealing position. Press the Manual button, on the High Pressure setting, and adjust the time to 15 minutes using the – and + buttons.
When it beeps allow the pressure to release naturally for 10 minutes, then turn the knob to release the rest and remove the lid.
Remove the chicken and place on a plate to shred. Skim the excess fat off the top of the chicken stock and add the peas, carrots, and tarragon.
Stir to combine. We are using the residual heat to heat the vegetables.
Whisk the warm milk and flour in a small bowl. Press the Cancel button, then the Saute button. Add the flour mixture to the pot and stir to combine.
Continue stirring until the soup starts to simmer and thicken. Adjust seasonings if necessary and serve.
Notes
If you do not like tarragon, substitute thyme or any other herb of your choosing.
If you use whole milk or cream, your soup will be much creamier and thicker than mine. CashewMilk does not have the same fat content and breaks apart more than regular milk does. I have used canned Coconut milk in the past, but it is still thinner than using heavy cream or whole milk...and tastes like coconut.
You can use frozen chicken breasts in this recipe, it will just take longer for the pot to come up to pressure. The cooking time is the same!!
I always use frozen peas and carrots. You can substitute fresh, but you will need to cook them under pressure for a minute or two to soften/cook them.
My two chicken breasts weighed one pound. If yours weigh less, you will need to adjust your time, about 1 minute per ounce.