Preheat the oven to 220°C/425°F/gas 7 and lay out a large sheet of thick tin foil (about 60cm long). Pile the rice onto one half of the foil. Halve and add the pak choi and tomatoes, then use a speed peeler to peel over the courgette in ribbons. Finely slice and scatter over the chilli (deseed if you like). Mix the curry paste with the coconut milk in a small bowl, then rub it all over the fish. Place the fish on top of the veg, pouring over the Thai green curry mixture, then add the soy and fish sauce. Arrange the lime around the fish and tear over the herbs. Season with sea salt and black pepper. Crack and separate the egg. Brush around the perimeter of the foil with egg white (save the yolk for another recipe), then fold in the foil overhang, tightly rolling the sides in towards the centre to seal. Carefully transfer the bag to a baking tray, then place the tray on the hob over a medium heat for 5 minutes, or until the bag starts to puff up. Bake on the middle shelf of the oven for 15 minutes, or until the fish is beautifully cooked through, then remove from the oven and leave to steam for 5 minutes. Delicious served with a seasonal salad, or an extra portion of steamed or roasted seasonal veg on the side.