Boil eggs in boiling water for about 8 minutes until hard. Drain, quench and peel. Wash and slice the tomatoes. Peel onion and cut into fine rings. Wash parsley, shake dry and pluck leaves from the stalks.
Finely puree the tuna and mayonnaise with the cutting stick.
Spread 4 slices of toast with the tuna cream, place the tomatoes, eggs, onions and parsley on top, cover with the remaining slices of toast. Halve the sandwich and arrange on plates.