Combine tomato sauce, Worcestershire sauce, soy sauce and mustard in a bowl. Set aside until required.
Cut each chicken breast in half horizontally to form 2 thin fillets.
Place flour on a plate. Season with salt and pepper. Whisk egg and 1 tablespoon of water in a shallow bowl. Place breadcrumbs on a plate. Toss 1 piece of chicken in flour to coat. Dip in egg mixture, then toss in breadcrumbs. Drizzle chicken with sauce and sprinkle with green onion. Serve with green salad, rice and lemon wedges.