To make the boudin, shell, trim and thoroughly wash the scallops. Dry well. Place in a blender or food processor along with the salt and the egg white and blend for a few minutes until you have a smooth paste. Rub the mixture through a sieve into a bowl set on crushed ice and mix in the paprika. Gradually add two-thirds of the cream, mixing in well. Add the vermouth and season. Test the mousse and if it is too firm, add a little more cream. Set aside in the refrigerator until needed.
Discard the stalks of the herbs, wash the leaves well, drain and finely chop. Using a 30 cm/12 inch roll of cling film, draw out about a 30-35 cm/12-14 inch sheet but do not cut it off. Sprinkle half of the chopped herbs over the cling film in an area about 20 cm/8 inches square. Divide the scallop mousse into 2 and gently place one half in an even line about 4 cm/1½ inches high, building a rough cylinder on top of the herbs along the edge nearest to you. Taking the end of the cling film, roll the mixture away from you across the herbs so that the mousse is completely coated. As you roll the mousse, leave the film on and continue rolling for another 30 cm/12 inches. Cut the roll off and tie up the ends tightly with string. You should now have a cylinder about 18-20 cm/7-8 inches long and 4.5-5 cm/1¾-2 inches across. Repeat the process with the remaining herbs and mousse. Bring a pan of water to the boil – the pan should be large enough to hold both rolls and deep enough for them to float freely. When boiling, plunge in the rolls, cover and simmer for 10 minutes. When cooked, remove from the pan and cool in iced water, still in the cling film, ensuring that they float clear so that they remain circular. Leave floating in iced water until needed.
To make the vinaigrette, blanch, skin and deseed the tomatoes, then cut them into 5 mm/¼ inch dice. Heat the oil in a saucepan, add the shallots and garlic and gently fry without colouring for about 1 minute. Add the tomatoes, tomato pureé, white wine, wine vinegar and bay leaf. Simmer over a low heat for 20 minutes. Remove from the heat and allow to go cold.