Heat the oil in a large shallow pan. Tip in the onion, parsnip and carrots, cover and gently fry for 8 mins until the onion is very soft.
Stir in the rice and bay leaf, then gently fry for another 2-3 mins until the rice starts to turn see-through around the edges. Add 300ml of the stock and simmer over a gentle heat, stirring until it has all been absorbed. Carry on adding the hot stock, a ladleful at a time, letting it be absorbed before adding more. Continue until the rice is just cooked and all the stock has been used, adding a little more water or stock if needed. This will take 18-20 mins.
Remove the bay leaf from the cooked risotto and stir in the peas. Heat through for a few mins, then add most of the Parmesan and season to taste. Sprinkle with the remaining Parmesan and serve.