Add in butter and oil over “high” on sauté. Brown your chicken for 2 minutes per side. Scoot the chicken to the side and add the onion and garlic, and sauté until fragrant, about 1 minute.
If you don’t have a sauté function, just add in the seasoned raw chicken, onion, and garlic (omit the butter and olive oil).
Pour in the chicken stock + cornstarch mixture, heavy cream, seasonings, and sun-dried tomatoes over the chicken.
Cover and use the slow cook function on High for 3 hours.
At this point, the chicken should shred with no resistance. Use two forks to shred it in the pot.
Stir in the parmesan. Add in the tortellini, submerging it in the liquid. Cover and continue to cook for another 15 minutes or until the tortellini is tender.
Toss in the fresh basil leaves and stir to incorporate. Turn to the “keep warm” function while serving. Garnish each bowl with additional Parmesan if desired.