Put the oil on to preheat - you want it to get to a steady 190C. Preheat the oven to 150c.
Prepare all the veg into bitesize chunks - cut the carrots / courgettes on the diagonal. Place on a chopping board ready to go.
Put the brown rice on to cook with the chicken stock cube. When convenient, fry and onion gently and add the peas or sweetcorn; set this to one side and stir through the rice once the rice is cooked and just being kept warm.
Make the batter by whisking everything together. Keep it as cold as possible; you can add an ice cube to the batter if you like.
Dip the vegetable pieces in the batter; shake off the excess and carefully add to the hot oil. Fry for about 2-3 minutes.
Remove from the pan and place on a baking tray lined with kitchen towel. Place in the oven (with the door open a crack - this will help keep the tempura cripsy) while you batch fry the rest of the vegetables. Don't try and do everything at once or the temperature of the oil will drop too much.
When all the veg has been fried, turn off the heat and carefully set the oil aside to cool.
Make sure you stir the fried onion and peas/corn through the rice. Season with soy sauce. Serve the tempura alongside the egg fried rice, and a little soy sauce for dipping (optional).