Set the cooker to SAUTE, HIGH. Heat half the oil. Cook the chicken, in two batches, for 3-4 minutes or until well browned. Set aside.
Heat the remaining oil. Cook onion, stirring, for 5 minutes or until tender. Stir in garlic and cook for 30 seconds or until fragrant. Stir in rice until opaque.
Return chicken to cooker with stock and wine. Stir to combine. Secure pressure cooker lid and set to PRESSURE, HI for 5 minutes. Quick release the pressure when done.
Remove the lid. Stir in parmesan and butter. Stand for 5 minutes, covered, allowing rice to absorb remaining liquid. Stir through spinach and season to taste. Serve with extra cheese.