egg foo young recipe

2 tbsp groundnut oil 150g protein of choice, such as raw king prawns (de-shelled and de-veined) or cooked chicken, cooked char siu pork or pre-fried tofu, cut into bite-sized pieces 1 small white onion, cut into strips 40g sliced mushrooms 40g peas ¼ tsp white pepper 4 eggs, whisked