Separate shrimp heads and shells from the meat and place them in bowls. Set shrimps aside in the refrigerator until ready to cook.
In a pot, bring water to a boil and add ginger, salt, and tahong. Cook until tahong shells have opened. Remove tahong and set aside.
Add shrimp heads and shells to the broth and smash the heads to release more flavor. Simmer for a few minutes and strain broth. Set aside.
In a large pot, melt butter and sauté onions then season with salt on medium-low heat until soft. Add chopped bacon and cook for a few minutes. Stir in potatoes until well coated. Sift in the flour and stir until well combined, making sure there are no lumps of flour. Cook for a few minutes.
Add stock, fresh milk, bay leaves, and kasubha. Boil until potatoes are tender.
Mix in pepper, sugar (optional), and heavy cream until well combined.
Mix in tahong. Add tanigue and shelled shrimp meat on top. Cover and cook for a few minutes, until fish is cooked. Serve hot!