Lightly grease a large baking sheet and sprinkle with a little water. On a lightly floured surface, roll out the pastry into a rectangle slightly less than 1/4 inch thick. Using a sharp knife, cut into six diamond shapes about 5 inches long. Transfer to the baking sheet. Brush pastry with egg glaze. Using the tip of a knife, score a line 1/2 inch from the edge, then lightly mark the center in a crisscross pattern.

Chill the pastry for 30 minutes. Preheat the oven to 425°F. Bake for about 20 minutes until puffed and brown. Transfer to a wire rack and, while still hot, remove each lid, cutting along the scored line to free it. Scoop out any uncooked dough from the bases and discard, then leave the pastry to cool completely.

In a large saucepan, bring the dry white wine and shallots to a boil over a high heat. Add the mussels to the pan and cook, tightly covered, for 4 - 6 minutes until the shells open, shaking the pan occasionally. Remove any mussels that do not open. Reserve six mussels for the garnish, then remove the rest from their shells and set aside in a bowl, covered. Strain the cooking liquid through a cheesecloth-lined strainer and reserve for the sauce.

In a heavy frying pan, melt the butter over medium heat. Add the scallops and shrimp, cover tightly and cook for 3 - 4 minutes, shaking and stirring occasionally, until they feel just firm to the touch; do not overcook.

Using a slotted spoon, transfer the scallops and shrimp to the bowl with the mussels and add any cooking juices to the mussel liquid.

To make the sauce, melt 2 tbsp of the butter in a heavy saucepan. Add the shallots and cook for 2 minutes. Pour in the fish stock and boil for about 15 minutes over high heat until reduced by three-quarters. Add the white wine and reserved mussel liquid and boil for 5 - 7 minutes until reduced by half. Lower the heat to medium and whisk in the remaining butter, a little at a time, to make a smooth thick sauce (lift the pan from the heat if the sauce begins to boil). Whisk in the cream and season with salt, if needed, pepper and lemon juice. Keep warm over very low heat, stirring frequently.

Warm the pastry bases in a warm oven for about 10 minutes. Put the mussels, scallops and shrimp in a large saucepan. Stir in a quarter of the sauce and reheat gently over low heat. Gently stir in the lobster meat and cook for 1 minute more.

Arrange the pastry bases on individual plates. Divide the seafood mixture equally among them and top with the lids. Garnish each with a mussel and a dill sprig and spoon the remaining sauce around the edges or serve separately.