Blanch the beans in boiling salted water for about 1 minute. Drain the beans and rinse briefly in cold water. Press the bean seeds out of the skin. Peel and roughly dice the onion
Heat butter in a pot. Sauté onion in it until translucent, add beans. Add stock and simmer covered for about 20 minutes. Add processed cheese, bring to the boil and puree to a creamy soup. Season to taste with salt and pepper
Whip the cream until semi-stiff. Arrange soup in glasses. Pour a cream stain on the soup and garnish with salmon caviar
Alternatively the soup can be served cold. Then cream and caviar should be added to the soup just before serving.