Clean the milkfish and pat it dry with paper towels. Fry the milkfish until golden brown. Set aside.
In a pan, heat a little oil over medium heat. Add the ginger and sauté until fragrant. Add the garlic and onion, and sauté until the onion becomes translucent.
Add the chopped tomatoes and cook until softened.
Stir in the rinsed tausi and cook for another 1-2 minutes, allowing the flavors to blend.
Add the fish sauce and black pepper. Stir well.
Pour in the water and bring it to a simmer then add the brown sugar. Let it simmer for about 5 minutes to allow the flavors to develop.
Carefully add the fried bangus to the sauce, spooning the mixture over the fish. Let it simmer for another 3-5 minutes, allowing the fish to absorb the flavors. Top with sliced green chilies for a bit of heat.
Adjust the seasoning if needed, adding more fish sauce or sugar to taste.
Transfer to a serving platter and enjoy your Bangus with Tausi with steamed rice.