Holding the squid firmly, pull the head from the body including internal parts and tentacles. Pull out the clear cartilage inside the tube and discard. With a knife, cut the head and the ink sack from the tentacles. Set aside the tentacles. Peel the spotted outer membrane from the squid and discard.
Under cold running water, wash the tentacles and the tubes inside and outside to remove any remaining tissue or debris. Drain well. Depending on size, cut squid into halves.
Under cold running water, wash crabs well. Scrub shells with a kitchen brush to rid of dirt and grime. Rinse and drain well.
In a large bowl of water, soak mussels for about 15 to 20 minutes. Rinse under cold running water to remove any dirt or grime on outer shells. Hold the beard (the brown thread sticking out between the shells) and pull it out towards the hinge end of the mussel. Rinse and drain well.
With scissors or knife, trim tendrils from shrimps. Rinse and drain well.
In a large pot over medium heat, heat oil. Add onions, garlic, and ginger and cook until softened.
Add shrimp paste and cook, stirring regularly, until lightly browned.
Add coconut cream and bring to a boil. Cook for about 10 to 15 minutes or until reduced and begins to curdle.
Add crab and cook until color changes.
Add mussels and cook until shells open.
Add shrimps and squid and cook until color changes to pink.
Continue to cook until sauce has thickened and reduced, clinging onto seafood.
Season with salt and pepper to taste. Serve hot.