Heat the vegetable oil in a frying pan. Add the chicken, cut into 1/2-inch cubes, and the onion, and sauté in order. Once cooked through, add the ketchup and stir-fry together.

Add the warm rice and quickly stir-fry over high heat, breaking up any clumps. Season with salt and pepper, then transfer to serving plates.

Beat the eggs. Add the milk to a frying pan and heat until it comes to a boil, then pour in all the beaten eggs at once.

Stir gently and cook until the eggs are just softly set, then pour over the chicken rice.

Heat the vegetable oil in a small saucepan. Add the mushrooms, cut into bite-sized pieces, and sauté.

Add the ketchup, Worcestershire sauce, water, and butter. Cook for 1–2 minutes until it comes to a boil and thickens slightly, then pour over the omurice.

Finish by drizzling with the milk.