Rinse rice in colander with cold running water. In large saucepan, bring water and salt to boil; add rice; reduce heat to medium low and simmer, covered 30 minutes. Drain. Meanwhile, in skillet, over medium high heat, fry bacon 3 to 5 minutes or until crisp. Transfer bacon to paper towel; pat dry and chop. Drain all but 1 tablespoon bacon drippings from skillet; add onions and cook, stirring 3 to 5 minutes or until tender. Add green pepper, celery and mushrooms; cook, stirring 3 minutes. Transfer vegetable mixture to 8 cup casserole. Stir in butter, beef stock and rice. Bake covered, 15 to 20 minutes in 180ºC degree oven until rice is tender. Season to taste with salt and pepper..