Debark the toast slices and roll out a little between 2 layers of foil. Drain tuna, puree and mix with Philadelphia. Peel onions and slice into fine rings. Clean iceberg lettuce, cut into fine strips, wash and drain carefully.
Spread slices of toast with the cream. Spread salad strips and onions on top. Cut the cress briefly and sprinkle on the slices. Halve the toast slices and fold them together. Serve 2 pieces in a napkin.