In a wok or sauté pan, heat a small amount of oil over high heat. Season the shrimp with salt and pepper. Sear them quickly on both sides just until they change color, being careful not to overcook. Transfer them to a plate.
Over medium heat, add the pork and a small amount of water. Spread the meat evenly in the pan and let it brown and crisp up as the fat renders out. Season with a pinch of salt. Once the pork is ready, move it to one side of the pan.
Sauté the ginger until lightly toasted. Add the garlic and onion, sautéing until softened.
Add the shrimp paste and sauté with the other ingredients.
Add the coconut milk, starting with 1½ cans, then stir everything together. Turn up the heat the heat and let it come to a boil. Scrape up any bits that have stuck to the bottom of the pan for added flavor. Add more coconut milk later as needed.
Add the kalabasa and chili peppers. Lower the heat and simmer until tender, about 15-20 minutes. Periodically check the kalabasa to prevent it from overcooking or becoming mushy.
Taste and season with fish sauce, salt, and pepper as needed. If the sauce appears too thick or dry, feel free to add more coconut milk or water.
Add the sitaw and shrimp, making sure the shrimp heads are submerged for thorough cooking. Cover and cook for an additional 2-3 minutes, until the sitaw is tender and the shrimp are fully cooked. Be careful not to overcook, as this can make the shrimp tough and the sitaw too soft. Turn off the heat.