In a medium skillet, combine the dry white wine, parsley, scallion, onion slices, bay leaf, peppercorns, a pinch of salt, and thyme.

Bring the mixture to a boil over high heat, stirring occasionally, until it reduces by half.

Add the water and the fish to the skillet and return it to a boil.

Reduce the heat to low, cover the skillet, and simmer for about 10 minutes, turning the fish once during cooking.

Once done, drain the liquid, remove the bay leaf, and let the fish cool.

Shred the cooled fish into a medium-sized bowl using your fingers.

To the shredded fish, add the finely chopped romaine lettuce and mayonnaise according to your taste preferences.

Season with a pinch of salt and freshly ground black pepper.

Cover the bowl and refrigerate the fish and lettuce mixture for at least 2 hours, allowing the flavors to meld together.