1. Sauté the thinly sliced shallots and leeks in olive oil. Add the beans and 2 cloves of garlic, coarsely chopped. Add the chicken broth.
2. Cook for 40 minutes.
3. At the end of the cooking time, add the cream and cook 10 minutes longer. Purée in a blender, strain and keep hot.
4. Reduce the balsamic vinegar over low heat.
5. Peel the raw langoustines. Sear them in olive oil in a skillet. Drain.
6. Ladle some of the cream of white bean soup into bowls and top with the langoustines and a ribbon of balsamic reduction. Garnish with chervil or dill.

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Photo: Isabelle Guégan. In collaboration with Canetti