Cook the rice in a pan of lightly salted boiling water together with the chopped carrots according to the instructions on the packet. Four minutes before the end of the cooking time, add the frozen peas. 

Meanwhile, heat the vegetable oil in a frying pan or wok, beat the egg together with a little salt, tilt the pan so that the egg coats the base and cook until set as a thin omelette.  Remove from the pan, roll up to form a sausage shape and cut into thin strips.

Add the butter to the wok and sauté the onion for two minutes. Add the cooked rice mixture, the soy sauce and a little freshly ground black pepper.  Stir fry the rice for about 2 minutes.  Stir in the strips of egg and spring onion and heat through.