Freshwater Crayfish with Fresh Herbs and Beurre Blanc

Name: Freshwater Crayfish with Fresh Herbs and Beurre Blanc (Petite marmite de queues d’écrevisses aux aromates)
Yield: For four people
Cuisine: French
Ingredients: 2—2½ kg (4½—5½ lb) live freshwater crayfish; 1 leek, white part only, cut into julienne strips; 1 teaspoon each of basil, tarragon and parsley, chopped; 1 teaspoon each of basil, tarragon and parsley, chopped; 1 teaspoon each of basil, tarragon and parsley, chopped; 1 teaspoon chives, snipped; 1 teaspoon chervil sprigs; 1 litre (1¾ pints) water; 300 g (10½ oz) carrots, cut into pieces; 2-3 onions, cut into quarters; 1 stick of celery, cut into pieces; 1 lemon, peeled à vif and sliced; 1 bouquet garni; 15 g (½ oz) whole peppercorns; 2 shallots; 1 tablespoon white wine vinegar; 4 tablespoons dry white wine; 3 tablespoons thick double cream; 150 g (5½ oz) butter, cut into dice; juice of half a lemon; salt, freshly ground pepper; salt, freshly ground pepper