Peal the shrimps and keep in the refrigerator.
Shortly pan fry the shrimp shells with the tomato paste in olive oil.
Rince and cut the vegetables (carrot, leek, onion, celery) in mirepoix (bigger cubes) and add to the shrimp shells. Glace with white wine and add water just enough to cover the ingredients. Leave to simmer for 30 minutes.
Cook the mussels or clams with a glass of white wine just done. Pour and pass through a sieve. Keep the liquid and add to the shrimp shells and vegetables.
Blender the soup and sieve.
Cook the soup again and let it reduce a little.
Add the cream, reduce again, stir and bring to the taste with salt, pepper and lemon juice.
Cut small croutons of the bread and leave to dry in the oven at 100ºC.
Take half of the clams or mussels out of their shell and add with the shrimps to the soup. Place the other half of the clams or mussels in a bowl and pour the hot soup over it. Serve with the croutons and a rouille.