Heat a non-stick frying pan, with a base is about 20cm in diameter. Add a little oil and a little butter. Once the butter is foaming, add in the prawns. Season and then sauté gently for 2-3 minutes. Remove to a plate and keep warm. Break the eggs into a bowl and add the water, chives and a little salt and black pepper and lightly beat. Add a little more oil and then a little butter to the pan, swirling it around so that the base and sides get coated. While the butter is still foaming, pour in half the egg mixture, tilting the pan from side to side. Stir gently with a fork or wooden spatula, drawing the mixture from the sides to the centre as it sets. When the eggs have almost set, scatter over half the pea and prawns. Cook for another minute or two then tilt the pan away from you slightly and use a palette knife to fold over the omelette. Slide on to a warmed plate. Repeat to make the second omelette. Serve at once with the rocket salad and some crusty bread.