Peel the cucumber. Remove the sausage from the skin. Cut sausage and cucumber into fine slices. Clean and wash spring onions, cut into thin, diagonal rings. For the marinade, wash, clean, quarter and seed the tomatoes. Cut the flesh into small cubes. Peel onion, dice finely.
Season vinegar with salt, pepper and sugar. Fold in the oil. Stir in tomatoes and onion. Mix salad ingredients and marinade. Spread slices of crispbread with cream cheese. Sprinkle with chervil and serve with salad