Turn on the Instant Pot and select sauté. Melt the butter, then add the onion, celery, and carrots. Cook for 3-4 minutes, stirring occasionally, until softened. Add the garlic and cook for 30 seconds, stirring constantly. Turn off sauté.

Add the potatoes, salt, pepper, and oregano to the pot. Pour in the vegetable broth and stir everything together.

Close the lid and set the steam release valve to sealing. Select manual/pressure cook and set the timer for 8 minutes on high pressure.

When the cooking time is done, let the pressure release naturally for 10 minutes. Carefully move the steam release valve to venting to release any remaining pressure. Once the steam is fully released, open the lid.

In a small bowl, whisk together the heavy cream and cornstarch until smooth. Stir the mixture into the soup.

Use a potato masher or immersion blender to mash or blend some of the potatoes, leaving some chunks for texture.

Turn the Instant Pot back to sauté and let the soup simmer for 3-5 minutes, stirring occasionally, until it thickens.

Serve the soup hot with optional toppings like shredded cheddar cheese, crumbled bacon, and chopped chives. Enjoy!