Crockpot Beef Chow Mein

1 (4 ounce) Can mushrooms
1 1/2 Pounds round steak, cubed
4 Stalks celery
2 Medium onions
1 Can water chestnuts, sliced
1 Cup hot water with 3 beef bouillon cubes
3 Tablespoons soy sauce
2 Teaspoons oyster sauce
2 Teaspoons Worcestershire sauce
1/8 Teaspoon ground ginger
1 Pound can Chinese vegetables
2 Tablespoons cornstarch
2 Tablespoons water

Cook on Low for 8 to 10 hours in crockpot. One hour before serving add Chinese vegetables, cornstarch and water.