For the filling, first steam the peas in a little salted water until soft. Blanch (scald) the tomatoes in boiling water, peel and cut into small cubes. Cut the spring onions into fine rings. Halve the chili pepper, remove the seeds and also cut into fine rings. Heat some oil in a wok or heavy frying pan and stir-fry the mince together with the spring onions and chilli. Stir in the tomatoes and peas and fry them as well. Season with soy sauce, fish sauce, pepper and brown sugar. Remove wok from heat and stir in chopped cilantro greens. Now beat the eggs and heat very little oil in a pan. Pour just enough of the beaten eggs to thinly cover the bottom of the pan. Fry until golden brown, turn carefully and cook the other side until just as golden. Gently lift out, transfer to a plate and keep warm. Bake the remaining omelets in the same way. Then spread some of the filling in the center of each omelet and fold the edges of the omelet in thirds on all four sides. (The filling in the center will remain partially open and visible.) Arrange on plates and serve.
If the omelet is served as a main course, it is served with cooked rice.