Step 1 Put potato cubes in a large saucepan of boiling water set over medium-high heat; cook for 12 minutes, or until very tender. Mash and set aside to cool. Meanwhile, put fish fillets, milk, bay leaf and peppercorns in a medium saucepan set over medium heat; bring to the boil. Reduce heat to low, cover and simmer for 4–5 minutes, or until fish is cooked. Transfer fish to a plate; discard milk, bay leaf and peppercorns. Set fish aside to cool, then flake.
Step 2 Combine mashed potato, flaked fish, lemon zest and spring onion. Divide mixture evenly to form 8 patties.
Step 3 Preheat oven to 200°C. Line a baking tray with baking paper. Mix flour and and freshly ground black pepper in a shallow bowl. Place egg and breadcrumbs in 2 separate shallow bowls. Dip patties into flour mixture one at a time; shake off excess flour. Dip patties into egg, then into breadcrumbs; press firmly to coat. Put patties on baking tray; spray with a light coating of oil. Bake patties for 20 minutes, or until crisp and golden.
Step 4 Meanwhile, make salsa: mix cucumber, dill and onion.
Step 5 Serve fishcakes with salsa, lemon wedges and salad.