Place the peeled, rinsed, and chopped cocoyam in a pot. Add water and cook for 20 minutes, until tender. Drain, then purée in a blender until smooth.
Put the sea snails in a pot with the stock cubes, cover with water, and cook for 20 minutes.
Add the fish, clams, sea snails, shrimp, and ground uziza. If required, top up the water and simmer until fully cooked.
Remove the fish from the saucepan and set aside.
Add the cocoyam in small chunks. Add the palm oil, yellow pepper, and bitter leaves.
Season with salt to taste.
Put the fish back in the soup pot. Stir, then cover and simmer.
When the mixture becomes a slurry and is no longer soupy or stew-like, remove from the heat. Serve with fufu as a side.