First prepare the dough. In a bowl mix flour with baking powder, sugar and salt. Make a well in the center of the flour and add egg, the sherry and the melted butter. Mix quickly with a spatula forming a smooth dough. Knead lightly and then place in the refrigerator for 1 hour. Place olive oil into a deep fryer and set at 370 degrees. Place mussels in a saucepan with 2 tablespoons dry white wine, cover with lid and place on heat, shaking from time to time - cook 2 minutes. Take mussels from shell, remove beard, finely slice mussels. Place clarified butter into a frypan and add green pepper and onion. Saute gently and then add raw shrimp and pimento - stir until shrimp is colored and then add crab and mussels. Season with salt, pepper and lemon thyme. Remove mixture from heat and allow to cool completely. Roll pastry dough out thinly. Cut pastry into 1 1/2-inch by 3-inch pieces. Brush with egg white and place a teaspoon of filling in the center of each. Dab your fingers in a little flour and fold pastry over and secure by pressing gently around edges. Drop 'empanadas' into the hot oil and cook 3 1/2 minutes or until puffed and golden. Turn them once. Place on serving dish and dust with freshly grated Parmesan cheese.