Heat the oil in a large saucepan or deep sauté pan over a high heat and fry the onion for 4–5 minutes, or until softened and lightly browned, stirring regularly.
Add the chicken to the pan and cook for 1 minute more, stirring. Add the rice and the stock, stir well then cover the pan with a lid and bring to a simmer.
Reduce the heat and simmer gently for 10 minutes, stirring occasionally until the rice is tender and saucy. You will need to stir more often towards the end of the cooking time to prevent the rice sticking. Add a splash of water if needed.
Stir in the peas and half the cheese and cook for 3 minutes more, or until the peas are hot, stirring constantly. Season to taste with a little salt if needed and lots of freshly ground black pepper. Serve the rest of the cheese separately for sprinkling on top.
