If using canned jackfruit, drain and rinse. Then, cut it into bite-sized pieces. If using fresh, take out the seeds and outer husk, then cut into bite-sized pieces.
Season the shrimp with salt and pepper. Over high heat, quickly sear them in a bit of oil but don't fully cook them. Transfer them to a plate.
In the same pan, add the pork and a little water. Cook over medium heat to brown and crisp the pork, allowing the fat to render out.Season with salt and add a bit more oil if needed. Once browned and crispy, push the pork to one side of the pan. Sauté the ginger until lightly browned. Add the garlic and onion, then sauté until softened. If you like some heat, add some sliced chilies at this point.
Add the shrimp paste and sauté with the aromatics and pork.
Add the langka and coconut milk, starting with 1½ cans, then stir everything together. Turn up the heat the heat and let it come to a boil. Add more coconut milk later as needed.
Place the whole chilies on top and simmer until the langka is tender for 20-30 minutes. Covering is optional; if you prefer a thicker sauce, leave it uncovered to allow some liquid to evaporate.
Season with fish sauce, salt, and pepper to your taste. If it appears too thick or dry, feel free to add more coconut milk or water.
Add the shrimp back and cook everything together until the shrimp is cooked just right. Taste and adjust the seasoning if necessary, then turn off the heat.