Set the Instant Pot to saute mode. When hot add oil.
Stir in chopped onion and garlic. Saute for a minute for the onion to soften and raw garlic smell has disappeared.
Add crumbled sausage to the pan. Brown it for 2 minutes.
Add crushed tomatoes, Tomato paste, Italian seasoning, chilli flakes, salt and 2 cups stock( reserve the rest to add later). Mix everything well (Scarp bottom of the pan to release any stuck brown bits)
Stir in dried tortellini.
Switch to Manual mode. Cover the lid. Set for 4 minutes on high pressure.
It will take around 5 minutes to come to full pressure and the timer to start.
When 4 minute ends, let the pressure release naturally for 5 minutes. Release rest of the pressure manually.
Once all the pressure is released, carefully open the lid.
Switch to sautee mode again. Add rest of the stock and half & half. Stir gently.
Let it cook for another 30 seconds or so. Switch off the pot.
Serve with grated parmesan and chopped parsley sprinkled on top.