In a bowl, combine ground beef with onion, salt and pepper.
Put-in the breadcrumbs and beaten egg then mix well.
Then scoop a mixture of beef and form into circle. Set aside.
Heat oil in a pan. Once the oil is hot, fry the meatballs until brown. Then remove some oil from the pan after frying.
On the same pan, using the remaining oil, saute garlic until brown.
Pour-in water and soy sauce, then add black pepper and bay leaf. Cook and let it boil for 5 minutes.
Then put-in the fried meatballs. Add the vinegar and beef stock, and simmer for 10 minutes.
Add the melted cornstarch and stir well for 3-5 minutes.
Transfer into a serving plate. Eat, share and enjoy!