Put a small nonstick frying pan on the hob to heat. Crack the eggs into a bowl, season with salt and pepper and add 1 tablespoon cold water. Beat with a fork until evenly mixed.
Add the butter to the pan. When it is foaming and melted pour in the beaten egg mixture. As the eggs begin to set, use a wooden spoon to draw the mixture into the centre of the pan, allowing the runny egg to flow to the edge of the pan.
When the top of the omelette is softly set arrange the chicken and cheese down the centre. Starting at the side nearest the handle, flip the omelette over the filling and then tip it out on to a plate. Cut in half and serve with a simple salad.