To make the tarator sauce, put the walnuts in a food processor and blend to a rough paste. Add the breadcrumbs, garlic, vinegar and a few tablespoons of cold water and continue to blend the mixture, slowly adding the olive oil in a steady stream until the oil is used up and the sauce is smooth.
Transfer it to a bowl and season generously with sea salt and freshly ground black pepper. Refrigerate until ready to use.
Place the fish and bay leaves in a small saucepan over medium heat and cover with water. Poach, uncovered, for 10–12 minutes or until cooked through. Drain the fish in a colander and place it in a large bowl. Break it into small pieces with a fork.
Soak the currants in a small bowl of warm water for 15 minutes, then drain them in a colander and add them to the bowl of fish, with the pine nuts.
Put the bread in a bowl of cold water and leave to soak for 5 minutes. Squeeze out the excess water with your hands and crumble the bread into the bowl with the fish. Add the spring onions, parsley, dill, dried mint and eggs. Season generously with sea salt and freshly ground black pepper.
Knead the mixture with your hands until all the ingredients are combined. Divide the mixture into 12 equal portions and shape into oval-shaped köfte. Spoon some flour onto a plate and roll the köfte in the flour.
Heat the oil in a frying pan over medium heat and fry the köfte in batches until golden on all sides, or for about 5 minutes. Drain them on kitchen paper, then transfer to a serving plate and serve with lemon wedges and the tarator sauce.