Take a shallow saucepan and pour in the vermouth and the fish stock, add the bay leaf and set to a simmering point. Poach the scallops for 1 minute and remove. Place into a colander over a bowl. Next add the fish and simmer for 2 minutes. Finally cook the prawns until pink. Add the poaching liquor to the drained liquid from the poached sea food. Now melt the butter in the same pan over low heat and cook the shallot and garlic until soft. Stir in the flour, and then gradually add the poaching liquor, stirring continuously. Cook for further 4 minutes. Stir in the lemon zest, capers, herbs and seasonings. Mix the fish and the potatoes into the sauce and pour into a 26 cm baking dish. Now take the puff pastry and over the pie dish, Brush with beaten egg, sprinkle with grated parmesan. Make a steam hole in the middle and decorate with pastry trimmings. Cook for 45 minutes at an oven temperature of 180°c. Leave to stand for about 5 minutes before serving.