Using a mortar and pestle, pound onion, garlic, and turmeric until a fine paste.
In a deep pan, heat cooking oil and saute the paste with 3/4 cup coconut cream, chili flakes, patis, bagoong, sugar, and pepper until reduced and well combined.
Place mixture in a bowl and add flaked galunggong, eggs, and remaining coconut cream, cornstarch, and water and pour into the bowl. Mix well and set aside.
Place the banana leaf containers in a steamer and pour the fish cake mixture in each. Steam for about 20 to 30 minutes. Serve hot.