Rinse matie fillets under cold running water, dab dry. Clean and wash the radishes. Peel, quarter and core the apple. Finely dice and mix the matie, radish, apple and gherkins.
Wash the chives, cut into small rolls and fold in. Season with pepper. Peel onions and cut into thin rings. Clean, wash and pat lettuce dry. Spread bread with fat and cut through diagonally once or twice depending on size.
Cover with lettuce leaves and spread the matyestatar on top. Garnish with onion rings.