Set your Instant Pot to sauté. Add 2-3 tablespoons of water, onion, carrots and celery and sauté until softened, about 5 minutes, adding more water if needed to prevent sticking.
Add all remaining ingredients, except the spinach and give it a stir. Lock your lid in place, ensuring the valve is set to the sealing position. Then set your Instant Pot to high pressure on high for 4 minutes. (It will take about 15 minutes to reach pressure.) Once complete, quick release, and stir in the spinach. Serve garnished with black pepper if desired.
Stove Top Directions
In a large pot, add 1-2 tablespoons of water, onion, carrots, and celery and sauté until softened, about 5 minutes. Add more water as needed to prevent sticking.
Then add all remaining ingredients, except the spinach, and bring to a boil. Lower the heat and simmer for about 20-25 minutes, adding the spinach in the last 5 minutes of cooking.