Cook macaroni in a large non-stick saucepan until al dente, according to instructions on the packet.
Meanwhile, heat oil in a large frying pan, add spring onions, sweetcorn, Chives, Celery Salt, White Pepper and Nutmeg. Stir-fry over a low heat for 3-4 minutes to allow the flavours to develop.
Pre-heat the grill to medium. Drain the cooked pasta and return it to the saucepan. Add the sweetcorn mix and the milk to the pasta and heat through until bubbling. Mix in the soft cheese and stir frequently until the cheese has melted and the sauce is reduced and creamy (about 5 minutes). Tip the mixture into a lightly greased flame-proof dish.
Top with sliced tomatoes, season with Garlic Pepper to taste and sprinkle cheese over the top. Drizzle over the Worcester sauce, if using, then grill under medium heat for 5-7 minutes, until golden brown.