Line 8 or 9 inch pie plate with half the pastry. Drain oil from tuna; put 1 tbsp. into saute pan. Add onion; saute until transparent. Add mushrooms; cook until onion and mushrooms begin to color. Add soup; stir until smooth. Remove from heat. Add cheese, lemon juice, and flavorings.
Arrange flaked fish and eggs in pastry shell. Pour sauce over; cover with remaining pastry. Crimp edges; make 1 or 2 slits in top to allow steam to escape. Bake in preheated 450 degree oven 10 minutes. Reduce heat to 350 degrees; bake 30 to 35 minutes, until pastry is well browned. Serve hot or cold. Yields 6 servings.
