mom's best beef chow mein casserole

Ingredients

• 1 - large onion, cut lengthwise
• 1 pound ground beef
• 1 1/2 cups water
• 1/4 cup soy sauce
• 1 can ben sprouts
• 1 1/2 cups celery cut into 1 inch pieces and then thinly sliced
• 2 tablespoons cornstarch
• 1 - beef bouillon, cubes