Fry the bacon in a pan without fat until crispy. Let it cool down briefly and break into small pieces. Put some pieces aside for garnishing. Peel the onion. Finely dice cucumber and onion.
Wash the dill, dab dry and pluck flags from the stems. Chop dill finely, except for a few flags for garnishing. Clean and wash spring onions and cut them diagonally into fine slices. Whisk the eggs and season with salt and pepper.
Pour half of the egg mixture into an ovenproof mould (20 x 20 cm). Set aside some spring onion, crabs and cucumber cubes for garnishing. Sprinkle the egg mixture with prawns, spring onion and dill.
Fill the remaining egg mixture into a second form (20 x 20 cm) and sprinkle with onion, bacon and cucumber. Place the forms in the fat pan of the oven. Fill the fat pan approx. 1 cm high with hot water and let it stand in the preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: level 2) for 12-15 minutes.
In the meantime clean, wash and spin-dry the salad. Toast slices roast and halve lengthwise. Wash parsley, dab dry and pluck leaves from the stalks. Cut out 4 ovals from each egg.
Cover each toast with a leaf of lettuce and a slice of egg. Garnish with prawns, spring onion, bacon, cucumber, parsley, dill and lemon.