Boil alimasag in water until color changes. Set aside and remove meat and set aside headshells.
Saute garlic, ginger, red onion, alamang, and siling labuyo. Mix in gata. Simmer until thick. Set aside.
Add crab meat and buko and season with pepper. You may season with sugar according to your liking.
Fill the crab shells with the meat mixture and top with bell peppers. Wrap in banana leaves and broil or grill until banana leaves are charred.