Finely chop 1 onion. Crush or finely chop 2 garlic cloves.
Thinly slice 5 oz button mushrooms.
Cut 10 oz chicken thighs into 1-inch chunks.
Prepare the risotto
Set Instant Pot to 'Sauté'. Add a drizzle of olive oil.
When it is hot, add the chicken and cook until starting to brown (approx. 3 minutes).
Add the mushrooms and cook until browned (approx. 5 minutes).
Add the onion, garlic, and thyme and cook until softened and fragrant (approx. 3 minutes).
Add 1 cup of arborio rice, and stir to coat with the liquid in the pan.
Add 2 cups of water, and crumble in 2 chicken stock cubes. Stir to release all the cooking residues from the pot, then allow it to come to the boil.
Pressure cook the risotto
When the risotto has come to the boil, press 'Cancel' to end the Sauté program.
Close and lock the Instant Pot lid. Ensure that the steam release handle valve is set to 'Sealing'.
Press the 'Pressure cook' button, and set it to pressure cook for 5 minutes.
When the time is up, use the quick release option to open the Instant Pot (press 'Cancel' then carefully turn the steam release handle to the 'Venting' position). When the float valve has dropped, open the Instant Pot.
Serve
Stir through 1 tablespoon of butter, then serve in bowls topped with the Parmesan cheese and arugula/rocket leaves.