Turn Instant Pot® on to sauté and heat oil. Add sausage and cook, stirring occasionally, until browned, about 3-5 minutes. Stir in onion and cook until tender, about 4 minutes. Add oregano and garlic; cook until fragrant, about 30 seconds.
Stir in bite-size potatoes and chicken broth. Close lid, set to sealing and set to manual high pressure for 8 minutes. When done cooking, do Natural Pressure Release (NPR) for 10 minutes. Release pressure.
Uncover, and turn Instant Pot® to sauté. Add spinach and cook until wilted, about 3 minutes. Stir in cream and cook until just heated through, about 5 minutes. Season soup with salt and pepper. Ladle soup into bowls, garnish with parmesan and serve.