Set the Instant Pot to sauté mode. Add olive oil, then add the chopped onion and garlic. Sauté for 2-3 minutes until fragrant.
Add the chicken pieces, salt, and black pepper. Cook for 2-3 minutes until the chicken is lightly browned.
Add the rinsed rice, chicken broth, and frozen mixed vegetables. Stir to combine, then secure the lid and set the valve to sealing.
Cook on high pressure for 8 minutes. Allow a natural pressure release for 5 minutes, then quick release any remaining pressure.
Open the lid and stir in the heavy cream and shredded cheddar cheese until well combined and creamy.
Serve hot, garnished with fresh herbs if desired.
