Put the stock in a large saucepan, add the rice and simmer for 35 minutes.
Meanwhile, heat the oil in a frying pan, add the onion and cook, stirring occasionally, for 5 minutes or until softened. Add the garlic, pumpkin and a little salt and pepper, mix together, then cover and cook over moderate heat for 10 minutes, stirring occasionally.
Drain the rice and reserve the cooking liquid. Stir the chopped herbs into the frying pan with the drained rice and grated Parmesan. Adjust the seasoning and moisten with the reserved rice liquid if necessary.
Spoon into shallow dishes and serve garnished with extra herbs and Parmesan shavings.