For your protein, preparation depends a little what you use. Cut the sausage thinly on the diagonal, or if using ham, dice in small chunks. If using pork belly, cut into thin strips. For chicken or tofu, dice relatively small. With any raw items - pork belly, chicken (and can do with tofu) - drizzle over a little soy sauce, rice wine and sugar and set aside to marinate as you prepare the rest.
The rice should be completely cooled before using. Separate the grains a little with your hands so it doesn't clump too much as you add it later. Thinly slice the white and the lower green part. Keep the white and pale green separate from the darker green slices.
Crack the egg into a small bowl and beat to break it up but without getting too much air in the egg - a chopstick is good for this. Measure out the other ingredients, or have them beside the stove with measures ready, before you start cooking.
Warm a wok or medium large skillet/frying pan over a medium-high heat then add the oil. Once warm, add the egg. Cook for a couple minutes until it is just cooked (if anything slightly under, it will cook a little more later). Break it up into small pieces with a spatula and remove from the wok/skillet, leaving the remaining oil.
If using pork belly/chicken/tofu, add this next and cook a minute or two. Then add the white and light green part of the spring onion, and if using sausage/ham, add this then. Stir and cook briefly so the onion softens. Add the rice and cook a minute or two, stirring regularly so the rice mixes through and becomes coated in the oil. Add a little extra oil if it's really sticking but don't add too much - you don't want it greasy so try to just use what's left, as far as possible.
Add the peas and add back the egg. Mix through and cook briefly, then add the white pepper and rice wine. Mix them through well. If it seems very dry, add a splash of water but it probably won't be needed. Remove from the heat and serve. Top with the thin green sliced spring onion (alternatively, you can add these in at the end shortly before serving).