For the chowder, pour the wine into a large, heavy-based, lidded saucepan and bring to the boil over a high heat. Reduce the heat until the liquid is simmering steadily, then add the clams and mussels and cover the pan with the lid. Simmer for 2-3 minutes, or until the shellfish have opened (discard any clams and mussels whose shells do not open during cooking).
Strain the shellfish through a fine sieve, collecting the cooking liquid in a separate saucepan. Suspend the shellfish over the pan; when cool enough to handle, pick all of the meat from the shells and reserve. Discard the shells.
Heat the butter over a medium heat in a saucepan measuring at least 26cm/10in in diameter. Fry the onion and garlic for 4-5 minutes, or until softened but not coloured.
Add the reserved cooking liquid and the bay leaf, 150ml/5fl oz water, cream and wakame, then bring the mixture to the boil. Once boiling, add the ginger, a grating of nutmeg (to taste) and the picked shellfish meats and heat through for a minute or so. Season, to taste, with salt, freshly ground black pepper, and a dash or two of lemon juice.
To serve, ladle the chowder into bowls and sprinkle a little chopped parsley over each serving. Serve a few baguette slices alongside, if using.