Preheat oven to 180 C / Gas 4. Grease a 2L (3 1/2 pt) casserole dish.
Pour the uncooked rice into the base of the prepared dish.
For the meatballs:
In a medium bowl, combine the egg, cheese and beef mince and mix well until the ingredients bind. Add the Worcestershire sauce and season with salt and pepper. Using your hands, mix thoroughly and roll the mince mixture into 10 meatballs.
Heat 2 tablespoons oil in a large frying pan and fry the meatballs until browned. Remove and place the meatballs over the rice in the casserole dish.
For the casserole:
In the same frying pan, add the onion and cook for 2 minutes until soft. Stir in soup, water, salt and pepper, mustard, garlic and herbs. Bring to the boil, stirring constantly. Remove from the heat and pour into casserole dish and cover.
Bake in the preheated oven for 45 to 60 minutes stirring occasionally to move the rice. Cook until meatballs are tender and no longer pink in the middle and the rice is soft.