Melt the butter in a large saute pan over medium heat. Add the chopped onion and fennel and cook for 10 to 15 minutes, until the onions are translucent. Add the flour and cook over low heat for 1 more minute, stirring occasionally.
Meanwhile, bring the stock to a simmer in a large saucepan. Add the shrimp and scallops and cook for 2 minutes, just until firm. Remove the seafood to a large bowl with a slotted spoon, reserving the stock.
When the flour is cooked in the onion and fennel mixture, slowly add the stock, the Pernod, salt, and pepper and simmer for 3 minutes. Stir in the heavy cream.
Cut the lobster meat into medium-size cubes and add it to the onion and fennel mixture with the shrimp and scallops. Add the frozen peas, frozen onions, and parsley and pour the mixture into a 9 by 13 by 2 baking dish.
For the pastry, mix the flour, salt, and baking powder in a food processor fitted with a steel blade. Add the butter and pulse 10 times, until the butter is the size of peas. With the motor running, add the ice water; process only enough to moisten the dough and have it just come together. Dump the dough on a floured surface and knead quickly into a ball. Wrap the dough in plastic and allow it to rest for 30 minutes in the refrigerator.
Meanwhile, preheat the oven to 375 degrees.
Roll the dough out to fit the baking dish with about 1/4-inch overlap. Use the egg wash to paint the outside rim of the dish. Place the dough on the filled baking dish and press it lightly to adhere to egg wash. Brush the dough with egg wash. Make 3 slashes in the top to allow the steam to escape. Place the dish on a sheet pan lined with parchment paper and bake for 1 hour and 15 minutes, until the top is golden brown and the filling is bubbling hot.