Heat oil in a pan.
Saute garlic and onion until brown.
Add the beef and cook for about 3-5 minutes. Then season with soy sauce and black pepper. Stir well and cook for another 5 minutes.
Then pour-in 4 cups of water, stir until it boils. Once the water boils, lower the heat and cover for 1 hour.
Add olive oil and Worcestershire sauce, then the remaining cups of water. Cover and let it boil for 20 minutes.
Put-in ampalaya or bittergourd and oyster sauce, then simmer for another 5 minutes while covered.
Then pour the melted cornstarch and stir continuously.
Transfer in a serving plate. Enjoy!