Place turkey breast into the pressure cooker and pour stock evenly over the top. Nestle the onion and celery around the edges. Sprinkle salt and pepper on top and add fresh thyme sprigs. Lock the lid and set to high for 25 minutes.
Naturally release pressure for 10 minutes before performing a quick release for any additional pressure. Before serving, check that the meat registers 165°F with an instant-read thermometer.
Slow Cooker Directions:
Use a 6-quart slow cooker. Place turkey breast into the slow cooker and pour stock evenly over the top. Nestle the onion and celery around the edges. Sprinkle salt and pepper on top and add fresh thyme sprigs. Cover and cook on low for 7-8 hours, or on high for about 6 hours. Before serving, check that the meat registers 165°F with an instant-read thermometer.