Turn Instant Pot onto saute. When hot, add sausage and garlic and cook until meat is browned.
When sausage is browned, add carrots, onion, and celery, and cook until fragrant (about 3-4 minutes).
Turn Instant Pot off and add salt, pepper, Italian seasoning, beef stock and tortellini. Turn Instant Pot on to manual high pressure for HALF the time it mentions on the back of the tortellini package. Mine said three minutes so I cooked it for 1 minute on manual high pressure.
When timer is up, quick release the pressure.
Turn Instant Pot off and then back onto saute.
Add evaporated milk and regular milk, heat until boiling. While milk is heating, mix together cornstarch and water.
When milk comes to a boil, add cornstarch mixture and stir well. Cook for another minute then turn Instant Pot off. Add the spinach and stir until wilted. Let soup sit for 2-3 minutes to thicken.